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в работе обоснованы структура и содержание процесса познания на основе научной картины мира (естественнонаучной, синергетической, предметных). Представлена модель естественнонаучной картины мира на основе принципов фундаментализации и генерализации. Обосновано, что образовательная система как синергетическая развивается в соответствии с закономерностями научного (учебного) познания.

Cavinula cocconeiformis (Gregory ex Greville) Mann & Stickle (Figs 2–31, 132–139) Basionym: Navicula cocconeiformis Gregory ex Greville (1855: 256, fig. 9: 6) Valves lanceolate to elliptic-lanceolate in smaller specimens with rostrate to broadly rounded apices. Valve length 12–25 (36) µm, width 7–11 (15) µm. Striae curved, radiate at center, to strongly radiate at apices, 25–30 in 10 µm; around central area striae alternate long and short. Striae uniseriate with fine rounded, to moderately elliptical areolae, which continue onto valve mantle. Internally, areolae positioned between thickened costae and covered with a raised hymen. Axial area narrow, linear to weakly lanceolate along valve length; central area not defined. Raphe distinct and central on valve. Externally, proximal raphe features tear-drop like; distal raphe features terminate on valve face, bent strongly or weakly in opposite directions at apices. Internally, proximal and distal raphe features terminate with helictoglossa. Copulae open bands, with two rows of pores. Type:— Elchies and various places in Banffshire, and latterly from Loch Leven (Gregory 1855: 256) (BM 566, “Braemar, Balfour, 8.54, no. 120” as Navicula nugax). “Elgin”, lectotype slide BM 689, lectotype designated here, BM 689. Observations:— Two morphotypes have been identified based on valve shape, distal raphe fissures and the presence of terminal areolae. Morphotype 1 has rounded to weakly rostrate apices with strongly deflected terminal fissures and no areolae in the terminal (apex) hyaline area (Figs 17–31, 136–139). Morphotype 2 (Figs 2–16, 132–135) has rostrate apices with weakly to strongly deflected distal raphe fissures and at least one series of areolae extending down the mantle at the apex (Figs 132, 133, 140). The specimens (morphotype 1), depicted as C. cocconeiformis resemble N. cocconeiformis (Greville 1855, fig. 9: 6) with a lanceolate valve outline and rostrate apices (Figs 28, 29). Slides in the Gregory collection are poorly made, labeled and indexed (Williams pers. com.). Greville’s slides are the next best thing as they were prepared from Gregory’s material. The slide clearly labelled in the Greville collection as N. cocconeiformis was BM 689 from Elgin. The Elgin locality was not listed in Greville’s original 1855 publication, but in 1856 Gregory (Notice of some new species of British freshwater Diatomaceae) lists the Elgin locality first in the “new species description and in the line drawing Gregory presents Navicula cocconeiformis under the section title “New species, now first named”. With this we feel confident that both Greville’s and Gregory’s concept of the species is depicted by specimens from Elgin and here designated as the lectotype. Morphotype 2 matches the line drawing of N. cocconeiformis (Gregory 1856, p. 6; pl. 1: 22) which in the figure legend states “new species, now first named”. Although it is tempting to create a new species from morphotype 2, without seeing SEM images of Gregory’s original syntype materials we cannot effectively discern which morphological form is C. cocconeiformis sensu stricto as intended by Gregory. DNA studies may assist in evaluating differences in these morphotypes. C. cocconeiformis is designated as the type species for the genus Cavinula (Mann & Stickle in Round et al. 1990) and morphotype 1, as presented, is considered representative of C. cocconeiformis sensu stricto. Krammer & Lange-Bertalot (1986, fig. 59: 2–5) depict valves representing morphotype 1 with a more rhombic outline and defined by the following valve features: L=12–40 µm, B=7–15 µm, and 24–36 striae in 10 µm. Morphotype 2 resembles the specimens presented in Siver et al. (2005, fig. 38: 1–3). They reported the following features for the population observed: valve length 21–26 µm, width 11–12 µm and stria density 24–28 in 10 µm. Foged (1971) documented C. cocconeiformis as a common taxon occurring in a small deep lake on the Northern Slope (Alaska), but states that “none of the presented illustrations represent the typical form” (Foged, 1971, fig. 15: 16, 18, 19). One of the specimens illustrated (Foged, 1971, fig. 15: 16) would match morphotype 2, while the other specimens are C. cocconeiformis f. elliptica (Foged, 1971, fig. 15: 18) and C. vincentii (Foged, 1971, fig. 15: 19). Morphotype 2 here noted, also resembles C. pusio (Cleve) Lange-Bertalot, but is distinguished by the deflected distal raphe ends and areolae extending down the mantle at the apex. Antoniades et al. (2008) reported specimens from the Arctic Archipelago for morphotype 1 (fig. 50: 7, 8) and morphotype 2 (fig. 50:10–12) with valve lengths 12–24 µm, widths 6–9.5 µm and stria densities 22–26 in 10 µm. C. cocconeiformis sensu lato can be distinguished from other Cavinula taxa by valve outline, the absence of a clearly defined central area, the strongly curved striae between valve center and apex, stria density and the deflected distal raphe endings in opposite direction at both valve apices. Distribution: —During our observations we confirmed the presence of C. cocconeiformis from White Pond (Ellesmere Island, Nunavut Territory), Maskinonge, St-Maurice, Lac aux Araignees and Madawaska (province of Québec), Lake Contwoyto and Lac De Gras (Northwest Territories, Singleton Lake, Clear Lake, Little Clear Lake, Sanschambre Lake, Ashigami Lake, Pedro Lake, Wawashkesh Lake, Crosson Lake, Laundrie Lake and Moot Lake (province of Ontario). In the CANA collection this taxon was identified from another 174 Canadian localities. C. cocconeiformis was also confirmed in the samples from Big Moose Lake, Pine Pond, Moriah Parch Pond and Santa Clara Green Pond (Adirondack Park, the state of New York, USA), and in 16 samples from ponds on Cape Cod. C. cocconeiformis was also tentatively identified in 316 + waterways across the United States (ANSP collection); however, voucher photomicrographs indicate that some of these identifications represent more than one taxon. We have verified the biogeographic distribution of C. cocconeiformis from Colorado to Maryland, extending north to northern Ellesmere Island and Greenland. Average weighted means for pH vary from 6.0 (northeastern United States) to 7.1 on the high Arctic Islands. The estimated weighted means for total phosphorus varied from 8.0 to 14.4 µg/L with a large error estimate. Conductivity values were low (Distribution Records:— Foged (1971, fig. 15: 16, 18, 19, Alaska), Foged (1974, fig. 17: 1–4, Iceland), Foged (1977, fig. 26: 14, Ireland), Krammer & Lange-Bertalot (1986: 158, fig. 59: 2–4, Europe), Watanabe (2005, fig. II B3- 18: 1–3, Japan), Antoniades et al. (2008: 47, fig. 107: 5, Arctic Archipelago), Potapova (2014, figs 211, 212, Bering Island, Kamchatka Peninsula, Russia)., Published as part of Cvetkoska, Aleksandra, Levkov, Zlatko, Hamilton, Paul B. & Potapova, Marina, 2014, The biogeographic distribution of Cavinula (Bacillariophyceae) in North America with the descriptions of two new species, pp. 181-207 in Phytotaxa 184 (4) on pages 183-185, DOI: 10.11646/phytotaxa.184.4.1, http://zenodo.org/record/5146714, {"references":["Greville, R. K. (1855) Report on a collection of Diatomaceae made in the district of Braemar by Prof. Balfour and Mr. George Lawson. The Annals and Magazine of Natural History 15: 252 - 261, 9 pls. http: // dx. doi. org / 10.1080 / 037454809495417","Gregory, W. (1856) Notice of some new species of British Fresh-water Diatomaceae. Quarterly Journal of Microscopical Science 4: 1 - 14.","Round, F. E., Crawford, R. M. & Mann, D. G. (1990) The diatoms. Biology and morphology of the genera. Cambridge University. Press, Cambridge, 747 pp.","Krammer, K. & Lange-Bertalot, H. (1986) Bacillariophyceae, 1. Teil: Naviculaceae. In: Ettl, H., Gerloff, J., Heynig, H. & Mollenhauer, D. (Eds.) Gustav Fischer, Stuttgart. Susswasserflora von Mitteleuropa (begrundet von A. Pascher) 2 / 1: 876 pp.","Siver, P. A., Hamilton, P. B., Stachura-Suchoples, K. & Kociolek, J. P. (2005) Diatoms of North America, the freshwater flora of Cape Cod, Massachusetts, U. S. A. Iconographia Diatomologica 14, 463 pp. http: // dx. doi. org / 10.1007 / s 10933 - 006 - 9041 - 6","Foged, N. (1971) Diatoms found in a bottom sediment sample from a small deep lake on the Northern Slope, Alaska. Nova Hedwigia 21: 1 - 114.","Antoniades, D., Hamilton, P. B., Douglas, M. S. V. & Smol, J. P. (2008) Diatoms of North America: The freshwater floras of Prince Patrick, Ellef Ringnes and northern Ellesmere Islands from the Canadian Arctic Archipelago. Iconographia Diatomologica 17: 649.","Foged, N. (1974) Freshwater diatoms in Iceland. Bibliotheca Phycologica 15: 1 - 192.","Foged, N. (1977) The diatoms in four postglacial deposits at Godthabsfjord, West Greenland. Meddelelser om GrOnland 199: 1 - 64, 8 pls.","Watanabe, T., Ohtsuka, T., Tuji, A., Houki, A. (2005) Picture book and ecology of the freshwater diatoms. Uchida-rokakuho, Tokyo, 666 pp.","Potapova, M. (2014) Diatoms of Bering Island, Kamchatka, Russia. Nova Hedwigia 143: 63 - 102."]}

Cavinula maculata Potapova, Cvetkoska, Hamilton & Levkov sp. nov. (Figs 193 –204) Valves elliptic-lanceolate with rounded apices. Valve face flat, sharply bent (not gradually curved) at margin onto mantle. Valve length 25–41 µm, width 15–20 µm with 20–25 stria in 10 µm. Striae radiate throughout; a few shortened striae may be present around central area. Striae uniseriate, composed of fine, rounded to elliptic areolae, 20–25 in 10 µm. Internally, interstriae slightly elevated and areolae covered with hymenes. Axial area narrow, linear. Central area large circular or transversely elliptic. Central nodule elevated internally. Raphe linear; externally, proximal and the distal raphe ends pinhole-shaped; distal raphe ends do not extend onto valve mantle (i.e. terminate on the valve face). Internally, raphe positioned on elevated sternum; distal raphe fissures terminate with a helictoglossa. Copulae open, with one row of pores. Type: — SOUTH CAROLINA, USA: Toms Creek near Gadsden, collection date: May 8, 1997, collected by B.L. Porter (holotype! slide ANSP GC59003, holotype! designated here, holotype specimen = Fig. 198; isotypes CANA 93669). Etymology: —The specific epithet (maculata) refers to the thickened central nodule that often appears as a dark spot in LM. Differential diagnosis:–– Cavinula maculata most resembles C. scutiformis in size, striae orientation, and enlarged and thickened central nodule. The valve outline of C. maculata is, however, elliptic-lanceolate rather than elliptic as in C. scutiformis, striae are much denser, and central area is conspicuously larger. The axial area is also narrower and linear. Areolae around central area in C. scutiformis are usually transversely elongated, while they are small and circular in C. maculata. Distribution:–– C. maculata is so far known from its type locality, Toms Creek, South Carolina, from Meyers Creek near Hopkins, South Carolina (ANSP sample GC024185, slide ANSP GC103271 a), and from Perkins Branch, Delaware (ANSP sample DE000158, slide ANSP GC 115038 b). Water chemistry data are available for two South Carolina sites. In 1997, when samples were collected, pH in these creeks ranged from 4.4–5.6, conductivity from 28–68 µS/cm, and nutrient concentrations were low., Published as part of Cvetkoska, Aleksandra, Levkov, Zlatko, Hamilton, Paul B. & Potapova, Marina, 2014, The biogeographic distribution of Cavinula (Bacillariophyceae) in North America with the descriptions of two new species, pp. 181-207 in Phytotaxa 184 (4) on page 203, DOI: 10.11646/phytotaxa.184.4.1, http://zenodo.org/record/5146714

Cavinula lapidosa (Krasske) Mann sensu lato (Figs 125, 126) Basionym: Navicula lapidosa Krasske 1929: 354, 7 Valves elliptical, with narrowing rounded apices. Valve length 13–18 µm, width 6–7 µm. Striae punctate, parallel to weakly radiate at the apices, 18–24 in 10 µm (measurements from Krasske material). Striae radiate throughout, curved at center and straight at apices. Areolae round barely visible in LM, 20–25 in 10 um. Axial area narrow linear, central area a bow-tie fascia with shortened striae along the margins. Raphe broad, linear; proximal fissures expanded, distal fissures deflect to opposite sides of the valve. Syntypes: –– Sachsen, Hessen (Germany), Chile. Lange-Bertalot et al. 1996, fig. 19: 22–26 (syntype). Observations:— In the original description three syntype localities were identified from Germany and Chile. The original line drawing illustrates an elliptic lanceolate valve with straight striae and a narrow raphe (morphotype 1, from Germany) while the LM images in Lange-Bertalot et al. (1996) from Chile are more elliptical with curved striae and a broader raphe with distinct proximal raphe fissures (morphotype 2). There appears to be either a broad variation in valve form or more likely different taxa. The specimen from Krasske’s material near Hessen, Germany, deposited at BRM N14/87a (Fig. 126) matches morphotype 1, while specimens from the southern USA (Fig. 125) more closely match morphotype 2. Cavinula lapidosa sensu lato is distinguished by the straight raphe with deflected terminal raphe fissures, the strongly radiate striae from center to apex and the bow-tie shaped central area with short striae of varying length along the margins. C. lapidosa can be compared to C. weinzierlii (Schimanski) Czarnecki, but is distinguished by bow-tie shaped central area, areolae formation, and the position of the proximal raphe fissure at the edge of the central area (compared to in the center of the central area in C. weinzierlii). Distribution:— Two records for C. lapidosa were reported in the CANA database from Ellef Ringnes Island and Axel Heiberg Island Arctic Archipelago. These specimens match morphotype 1 with an elliptic lanceolate valve and broad bow-tie shaped central fascia. In the ANSP collection, 16 sites from across the USA were identified to have C. lapidosa. The sites in the southern USA are linked to morphotype 2. As currently documented, this taxon has a wide latitudinal distribution from the north and southern hemispheres, more specifically across all of North America. Distribution Records:— Lange-Bertalot et al. (1996, fig. 19: 22–26, syntype, Chile), Krammer & Lange-Bertalot (1986, fig. 73: 5, 6, Europe)., Published as part of Cvetkoska, Aleksandra, Levkov, Zlatko, Hamilton, Paul B. & Potapova, Marina, 2014, The biogeographic distribution of Cavinula (Bacillariophyceae) in North America with the descriptions of two new species, pp. 181-207 in Phytotaxa 184 (4) on pages 189-192, DOI: 10.11646/phytotaxa.184.4.1, http://zenodo.org/record/5146714, {"references":["Krasske, G. (1929) Beitrage zur Kenntnis der Diatomeenflora Sachsens. Botanisches Archiv 27: 348 - 380.","Krammer, K. & Lange-Bertalot, H. (1986) Bacillariophyceae, 1. Teil: Naviculaceae. In: Ettl, H., Gerloff, J., Heynig, H. & Mollenhauer, D. (Eds.) Gustav Fischer, Stuttgart. Susswasserflora von Mitteleuropa (begrundet von A. Pascher) 2 / 1: 876 pp."]}

Cavinula scutiformis (Grunow ex A. Schmidt) Mann & Stickle (Figs 107–111) Basionym: Navicula scutiformis Grunow in Schmidt et al. 1881, fig. 70: 62 Valves elliptic, with rounded apices. Valve length 23–32 µm, width 17–22 µm. Striae radiate throughout valve length. Striae composed of fine, elliptic to somewhat rounded areolae, 12–14 in 10 µm. Stria density, 18–24 to 28–30 in 10 µm. Central area narrow, linearlanceolate, transforming into a defined central space transversally elongated, rounded to elliptical in shape. Central area formed by gradual shortening of striae along both valve margins. Raphe system linear; proximal raphe fissures tear-drop like. Distal raphe fissures pore-like and small, terminating on valve face. Type:— Stavanger, Norway. Grunow in Schmidt et al. 1881, fig. 70: 62 (holotype). Observations:— This taxon is identified by the elliptic valve shape, large transversely elongated central area, high stria and areola densities at the apices, and the presence of distinct pore-like fissures at the valve apices. Distribution:— C. scutiformis occurs in the northern regions of Europe, Asia and North America. In the CANA collection this taxon was identified from 35 localities in western (excluding Saskatchewan, Manitoba) and eastern Canada, but not from the tundra region north of 60 degrees. In the framework of this study, C. scutiformis was identified in six more localities from Canada, in which it was previously not recorded: sediment core C2 (50–51 cm) recovered from Flower Round Lake, Crosson Lake Oakley (sediment core) Muskoka District, Clear Lake Oakley (sediment core), Muskoka District, (Ontario) and additionally Big Moose Lake, Moriah Parch Pond (New York) and Walden Pond (Massachusetts) in the United States. This taxon was also confirmed in Lac aux Araignees (Québec). C. scutiformis was identified in samples with low to circumneutral pH (5.1–7), an average weighted mean conductivity of 34.5 µS/cm, with a range of 26–65 µS/cm, and an average weighted mean alkalinity of 62 µeq/L, and a range between 6 and 153 µeq/L. Distribution Records:— Grunow in Schmidt et al. (1881, Atlas der Diatomaceen-kunde, Band I, Serie I-III, fig. 70: 62), Krammer & Lange-Bertalot (1986, fig. 59: 10, 11, Europe), Lange-Bertalot & Metzeltin (1996, fig. 24: 13, 14, fig. 114: 3, 4, Europe), Foged (1971, fig. 15: 20, Alaska).

Cavinula kernii Cvetkoska, Hamilton, Levkov & Potapova sp. nov. (Figs 181 –192) Valves elliptic-lanceolate with rounded apices. Valve face flat, sharply bent (not gradually curved) at margin onto mantle. Valve length 14–17 µm, width 7–8 µm with 22–24 stria in 10 µm. Striae radiate throughout; short and long striae alternate around central area. Striae uniseriate, composed of fine, rounded to elliptic areolae, 25–30 in 10 µm. Internally, areolae positioned between thickened costae and covered with hymenes. Axial area narrow, linear, transforming into a small rounded central area. Raphe linear, externally, proximal and the distal raphe features small pores; distal raphe endings do not extend onto valve mantle (i.e. terminate on the valve face). Internally, raphe positioned on elevated sternum; both, proximal and distal raphe fissures terminate with a helictoglossa. Copulae open, with one row of pores. Type: — CALIFORNIA, USA: Kern River, Kernville, collection date: September 13, 1993, collected by B.L. Porter (holotype! slide ANSP GC 101724 b, holotype! designated here, Accession No. ANSP GC 101724 b, holotype specimen = Fig. 185; isotypes: CANA 105729). Etymology:–– The specific epithet (kernii) refers to the type locality, Kern River. Differential diagnosis:–– Cavinula kernii most resembles C. mollicula Hustedt in valve outline and structural form (Lange-Bertalot & Metzeltin (1996, fig. 24: 10–12, fig. 114: 5). There are minor differences in valve outline (more linear in C. kernii), central area (more evident in C. kernii), and the absence of scattered areolae at the terminal nodule (scattered pores present in C. mollicula). Lange-Bertalot also proposed that Navicula orbis Carter and Navicula arenula Hohn & Hellerman are synonymous with C. mollicula, which suggests that a number of similar taxa need to be considered in a more complete examination of this group of valve forms. C. cocconeiformis f. elliptica is also similar in valve shape and size. C. kernii is distinguished by the simple poroid (not deflected) terminal raphe fissure. In addition there is an isolated row (ca. 12 areolae) along the base of the mantle of C. kernii and no other areolae in the terminal area, in contrast to C. cocconeiformis f. elliptica which has larger areolae along the base of the mantle that continue around the margin of the valve and there are additional areolae scattered in the terminal area. The significance of these differences between C. kernii and C. cocconeiformis f. elliptica need further investigation. C. kernii also resembles the smaller valves of C. davisiae but easily differentiated by the small (versus large round in C. davisiae) central area, distal fissures not hooked (deflected in opposite direction in C. davisiae), sharp bend at the valve margin (versus more gently rounded in C. davisiae), and the lower stria density, (22–24 versus 26–32 in 10 µm in C. davisiae). Another similar taxon is C. thoroddsenii (Foged) Lange-Bertalot (see: Foged, 1974, fig. 17: 7–10). Cavinula kernii is differentiated by a smaller valve size (L=19–31 µm, W=11–13 µm in C. thoroddsenii), and the small rounded central area versus apically elongated central area in C. thoroddsenii. C. hilliardii (Figs 112–122) differs by the valve shape and the orientation of striae (for comparison also see Foged 1971, fig. 14: 18). Distribution:— So far, this taxon (sensu stricto) was only observed in the samples from the type locality, Kern River, Kernville, California, USA. In July 1992, the pH was 8.4 with a specific conductance of 158 µS/cm.

Cavinula jaernefeltii (Hustedt) Mann & Stickle (Figs 82–92, 146–151) Basionym: Navicula jaernefeltii Hustedt 1936 (in Schmidt 1874 –1959) Valves elliptical, rounded in smaller specimens. Hustedt’s original description (1942), valve length 12–20 µm, width 7–11 µm, with 25–30 striae in 10 µm. Populations in this study: length 8–17 µm, width 5–9 µm, with 20–24 striae in 10 µm. Striae parallel in center, more radiate towards poles. Striae uniseriate, small areolae barely discernable in LM observations. At center one or more short striae. Internally, areolae between thickened costae, covered with hymen. Axial area narrow, linear, with small central area. Raphe straight, externally positioned within depression; distal and proximal raphe ends enlarged, not curved. Distal ends terminate on valve face. Internally, raphe with raised sternum. Type: — Wuokatti, Finland. Simonsen 1987, fig. 308:1–5 (lectotype). Here presented in Fig. 84 from slide BRM N12 /84. Observations:— Cavinula jaernefeltii is distinguished from other small Cavinula taxa by the valve shape, the shape of the axial area, the smaller areolae, and by the raphe formation, especially the position of the terminal raphe fissures away from the apex mantle on the valve face. The striae of C. jaernefeltii also appear to be finer, less punctate and less radiate than similar small forms of Cavinula hilliardii, typically making distinctions of this form from other Cavinula taxa relatively straightforward. However, there is a large range in valve forms from elliptical to linear-elliptical, and water chemistry optima, which may suggest more than one taxon is present within this group. Also compare with C. intractata (Hustedt) Lange-Bertalot, a taxon with narrowly rounded to cuneate ends and more radiate striae. Specimens identified as C. mollicula from Finland by Lange-Bertalot & Metzeltin (1996, fig. 24: 10–12) are also comparable but more similar to C. cocconeiformis f. elliptica sensu stricto which has a higher stria density, different raphe formation, and more consistent elliptical valve outline. Distribution:— A total number of 77 records for C. jaernefeltii were reported in the CANA database from across North America, 69 of which originate from different localities in Canada and 8 samples were collected in Massachusetts, United States. During our LM observations, the presence of this taxon in North America was verified in the following localities: Ashigami Lake, Lake Abitibi, Moot Lake, Wawashkesh Lake in the province of Ontario; two localities in the Québec province: Madawaska and Maskinonge; Hilltout Lake in British Columbia; Baffin Island in Nunavut and another station in the Yukon Territory. During the observation of slides from Massachusetts, C. jaernefeltii was not verified. In the ANSP collection, C. jaerenfeltii was identified in different localities across South Carolina, Virginia, California, Colorado, Delaware, Indiana and Wisconsin. However, during our observation of a number of diatom slides from these localities, we did not confirm the presence of C. jaernefeltii. The southern distribution of C. jaernefeltii is restricted to Canada and the northern United States. C. jaernefeltii appears in oligotrophic waters which are mildly alkaline to acidic.A single locality in the Arctic with mildly alkaline waters (pH 8.3) had a population which represented 54% of the community (Antoniades et al. 2008). Distribution Records:— Simonsen (1987, pg. 198, lectotype, fig. 308: 1–6, Finland), Antoniades et al. (2009: 61, SEM type material: 65–68, Arctic Archipelago), Metzeltin & Witkowski (1996, fig. 2: 42–44, Bear Island, Svalbard), Watanabe (2005, fig. II B -18: 5–9, Japan), Foged (1974, fig. 17: 13, Iceland), Potapova (2014, fig. 210, Bering Island, Kamchatka Peninsula, Russia)., Published as part of Cvetkoska, Aleksandra, Levkov, Zlatko, Hamilton, Paul B. & Potapova, Marina, 2014, The biogeographic distribution of Cavinula (Bacillariophyceae) in North America with the descriptions of two new species, pp. 181-207 in Phytotaxa 184 (4) on pages 188-189, DOI: 10.11646/phytotaxa.184.4.1, http://zenodo.org/record/5146714, {"references":["Schmidt, A. (1874 - 1959) Atlas der Diatomaceen-kunde. R. Reisland, Leipzig.","Simonsen, R. (1987) Atlas and catalogue of the diatom types of Friedrich Hustedt, vol. l - 3. J. Cramer, Stuttgart, Germany, 525 pp, 772 pls.","Lange-Bertalot, H. & Metzeltin, D. (1996) Indicators of oligotrophy, 800 taxa representative of three ecologically distinct lake types: Carbon buffered - oligodystrophic - weakly buffered soft water. Iconographia Diatomologica 2: 390.","Antoniades, D., Hamilton, P. B., Douglas, M. S. V. & Smol, J. P. (2008) Diatoms of North America: The freshwater floras of Prince Patrick, Ellef Ringnes and northern Ellesmere Islands from the Canadian Arctic Archipelago. Iconographia Diatomologica 17: 649.","Antoniades, D., Hamilton, P. B., Hinz, F., Douglas, M. S. V., Smol, J. P. (2009) Eight new species of freshwater diatoms (Bacillariophyceae) from the Canadian Arctic Archipelago. Nova Hedwigia 88: 57 - 80. http: // dx. doi. org / 10.1127 / 0029 - 5035 / 2009 / 0088 - 0057","Metzeltin, D. & Witkowski, A. (1996) Diatomeen der Baren-Insel. Iconographia Diatomologica 4: 232.","Watanabe, T., Ohtsuka, T., Tuji, A., Houki, A. (2005) Picture book and ecology of the freshwater diatoms. Uchida-rokakuho, Tokyo, 666 pp.","Foged, N. (1974) Freshwater diatoms in Iceland. Bibliotheca Phycologica 15: 1 - 192.","Potapova, M. (2014) Diatoms of Bering Island, Kamchatka, Russia. Nova Hedwigia 143: 63 - 102."]}

Cavinula variostriata (Krasske) Mann in Round et al. 1990 (Figs 123, 124) Basionym: Navicula variostriata Krasske 1923, 197: 12 Valves linear, with rounded apices. Valve length 30–32 µm, width 7–8 µm. Striae curved and radiate throughout valve length. Stria density 24–27 in 10 µm. Axial area narrow and linear. Central area rectangular to broadly rounded, extending to valve margin with reduced marginal striae. Central area forms a large internally expanded nodule. Raphe linear; proximal raphe fissures externally small teardrop like; internally proximal fissures weakly deflected in opposite directions and terminal fissures ends with small helictoglossae. Distal raphe fissures externally deflected in opposite directions and terminate on valve face. Areolae round to elliptic externally and internally. Internal areolae openings covered by hymen. Type:— Hessen, Germany. Observations:— This taxon is identified by the linear valve margins, large central area, evident internally expanded central nodule, and the oppositely deflected terminal raphe fissure that do not extend down the mantle. Distribution:— Cavinula variostriata occurs in the northern regions of Europe, and North America. In the CANA collection this taxon was identified from 26 localities from Axel Heiberg Island, Ellesmere Island, Baffin Island (Arctic Archipelago), Lac Karinbou (northern Québec) and unnamed lakes in central Ontario. In the USA, C. variostriata was tentatively reported from 13 locations but to date only samples from Murder Creek (New Jersey), Red Mill Pond (Delaware) and Johnson Creek (Montana) have been verified. Specimens from New Jersey and Delaware are more elliptical in shape and the central area is smaller compared to specimens from the Arctic Archipelago. C. variostriata needs a more detailed study in North America. Distribution Records:— Lange-Bertalot et al. (1996, fig. 18: 27–30, Europe), Krammer & Lange-Bertalot (1986, fig. 59: 10, 11, Europe), Güttinger (1991, fig. 2.05: 31–34, Great Britain), Foged (1974, fig. 13: 8, 9, Iceland), Potapova (2014, fig. 214, Bering Island, Kamchatka Peninsula, Russia)., Published as part of Cvetkoska, Aleksandra, Levkov, Zlatko, Hamilton, Paul B. & Potapova, Marina, 2014, The biogeographic distribution of Cavinula (Bacillariophyceae) in North America with the descriptions of two new species, pp. 181-207 in Phytotaxa 184 (4) on page 198, DOI: 10.11646/phytotaxa.184.4.1, http://zenodo.org/record/5146714, {"references":["Round, F. E., Crawford, R. M. & Mann, D. G. (1990) The diatoms. Biology and morphology of the genera. Cambridge University. Press, Cambridge, 747 pp.","Krasske, G. (1923) Die Diatomeen des Casseler Beckens und seiner Randgebirge nebst einigen wichtigen Funden aus Niederhessen. Botanisches Archiv 3: 185 - 209.","Krammer, K. & Lange-Bertalot, H. (1986) Bacillariophyceae, 1. Teil: Naviculaceae. In: Ettl, H., Gerloff, J., Heynig, H. & Mollenhauer, D. (Eds.) Gustav Fischer, Stuttgart. Susswasserflora von Mitteleuropa (begrundet von A. Pascher) 2 / 1: 876 pp.","Guttinger, W. (1991) Collection of SEM micrographs of diatoms, Series 5. Pura, Switzerland 48 pls.","Foged, N. (1974) Freshwater diatoms in Iceland. Bibliotheca Phycologica 15: 1 - 192.","Potapova, M. (2014) Diatoms of Bering Island, Kamchatka, Russia. Nova Hedwigia 143: 63 - 102."]}

Cavinula scutelloides (W. Smith) Lange-Bertalot (Figs 101–106, 165–171) Basionym: Navicula scutelloides W. Smith 1856 (in Synopsis of British Diatomaceae, Vol. 2, 107, figs: 32–60, 61–62) Valves elliptical, to round in smaller specimens with widely rounded apices. Valve length 12–26 µm, width 9.5–20 µm. Striae radiate, 8–10 in 10 µm, uniseriate with coarse elliptic to rounded areolae. Areolae internally occluded with hymen. Central area can be transversely expanded on one side. A few short striae present around valve center; all striae continue on mantle. Axial area narrow, linear-lanceolate. Raphe system linear; externally, proximal raphe features tear-drop like on valve face. Distal raphe fissures bent in the same direction, question mark-like, terminating on the valve mantle. Internally, raphe positioned on elevated sternum. Proximal raphe features curved in same direction, hook-like, and distal raphe features terminate with helictoglossae. Type:––Omersby, Norfolk, United Kingdom. Here presented in Figs 103, 104 (type material). Observations:— This taxon is identified (Figs 103, 104 from type material) based on shape, size and the enlarged areolae on the valve face. The closest taxon to compare with would be C. pseudoscutiformis, however they are separated by shape of proximal raphe fissures, length of alternating striae around the central area, and areolae size, and orientation. In addition, C. scutelloides and C. pseudoscutiformis are found under different water acidity conditions. Distribution:— Currently this taxon is recognized as a cosmopolitan species across the temperate zone of the northern hemisphere, and relatively absent from the northern tundra with the possible exception of a small deep lake from northern Alaska (Foged 1971). C. scutelloides was identified in 26 samples in the CANA database. According to those identifications, this taxon is present in the central part of North America e.g. the province of British Columbia, Ontario, Quebéc (Canada) and New York and Massachusetts (USA). The absence of C. scutiformis in the slides and samples in which they were reported, led us to the conclusion that specimens of C. scutelloides were often identified as C. scutiformis. Accordingly, C. scutelloides was verified from the following localities: Low Water Lake (Sudbury District, Ontario), Singleton Lake (southern Ontario), Flower Round Lake (southern Ontario), Hawkins Lake (Interior Douglas Fir, British Columbia) and Sneezie Lake (Cariboo Aspen-Lodgepole pine, British Columbia), Canada. In the northern United States verified specimens were observed from Walden Pond Massachusetts and Queer Lake (Adirondack Park, New York). Searches in the data from ANSP, indicated that C. scutelloides was identified from central North America in the states of Wisconsin, Maine, Georgia, Indiana, Iowa, Connecticut, Michigan, Illinois, Idaho and Minnesota. C. scutelloides is absent in low pH water bodies, found from Florida to the high Arctic. However, in circumneutral to alkaline environment it was often observed. In western Canada, C. scutelloides was found to occur in lakes with a TP range of 7–39 µg /L (Cumming et al. 1995). Distribution Records:— Krammer & Lange-Bertalot (1986, fig. 59: 16–19, Europe), Levkov et al. (2007, fig. 68: 1–4, fig. 68: 6, fig. 69: 5, Europe), Watanabe (2005, fig: II 2B 3 -18: 16, 17, Japan), Foged (1971, fig. 15: 21, 22, Alaska)., Published as part of Cvetkoska, Aleksandra, Levkov, Zlatko, Hamilton, Paul B. & Potapova, Marina, 2014, The biogeographic distribution of Cavinula (Bacillariophyceae) in North America with the descriptions of two new species, pp. 181-207 in Phytotaxa 184 (4) on page 196, DOI: 10.11646/phytotaxa.184.4.1, http://zenodo.org/record/5146714, {"references":["Foged, N. (1971) Diatoms found in a bottom sediment sample from a small deep lake on the Northern Slope, Alaska. Nova Hedwigia 21: 1 - 114.","Cumming, B. F., Wilson, S. E., Hall, R. I. & Smol, J. P. (1995) Diatoms from British Columbia (Canada) lakes and their relationship to salinity, nutrients and other limnological variables. Bibliotheca Diatomologica 31: 1 - 207.","Krammer, K. & Lange-Bertalot, H. (1986) Bacillariophyceae, 1. Teil: Naviculaceae. In: Ettl, H., Gerloff, J., Heynig, H. & Mollenhauer, D. (Eds.) Gustav Fischer, Stuttgart. Susswasserflora von Mitteleuropa (begrundet von A. Pascher) 2 / 1: 876 pp.","Levkov, Z., Krstic, S., Metzeltin, D. & Nakov, T. (2007) Diatoms of Lakes Prespa and Ohrid. About 500 taxa from ancient lake system. Iconographia Diatomologica 16: 603.","Watanabe, T., Ohtsuka, T., Tuji, A., Houki, A. (2005) Picture book and ecology of the freshwater diatoms. Uchida-rokakuho, Tokyo, 666 pp."]}

Cavinula hilliardii Manguin ex Kociolek & Reviers (Figs 112–122) Basionym: Navicula hilliardii Manguin ex Kociolek & Reviers 1996 Valves linear to linear-elliptic with broadly rounded apices. Valve length 16–26 µm, width 8–10 µm. Striae punctate, parallel to weakly radiate at the apices, 18–24 in 10 µm. Striae sometimes curved towards apices. Areolae round, easily visible in LM, 25–30 in 10 um. Axial area narrow linear, central area absent to weakly defined. Raphe broad, slightly curved towards proximal raphe fissures; proximal fissures weakly expanded, distal fissures deflect to opposite sides of the valve. Type: –– Lake Karluk, Alaska. Manguin 1960, fig. 2: 7 (holotype line drawing) Observations:— Cavinula hilliardii is a rare species presently confirmed from LM images. The valves are linear to linear-elliptical, and the lower density of areolae is distinctive for this taxon. In LM, the raphe is broad, easily visible and has some similarity to C. jaernefeltii. The lower areola density and the curved terminal raphe fissures separate this taxon from C. jaernefeltii. Distribution:— Currently identified from the Arctic, Alaska, Axel Heiberg Island in the Arctic Archipelago. Based on the observations of Foged (1981) and this study, C. hilliardii has a more restricted northern distribution in oligotrophic and alkaline habitats across the Arctic and Alaska. Distribution Records:— Manguin (1960, fig. 2: 7, line drawing, Alaska), Foged (1981, fig. 30: 9–11, Alaska).

Cavinula pseudoscutiformis (Hustedt) Mann & Stickle (Figs 44–73, 152–164) Basionym: Navicula pseudoscutiformis Hustedt 1930, p. 291, fig. 495 Valves rounded to slightly elliptical in larger specimens, with broadly rounded ends, not differentiated from valve body. Valve face flat, curving abruptly into a shallow mantle. Valve length 4.5–13 (17) µm, width 4–11 (14) µm. Axial area narrow, almost linear, transforming into a small elliptical, transapically elongated and unilaterally slightly expanded central area. Striae around central area alternate, short and long. Internally, axial area with slightly thickened lanceolate ridge. Raphe filiform; proximal and distal raphe endings slightly deflected in the same direction on the valve face. Central raphe endings larger than distal ends with tear-drop like central pores encircled with silica ridge. Deflected raphe endings, especially in smaller specimens, not clearly discernable in LM. Striae uniseriate, strongly radiate throughout, 21–24 in 10 µm. Each stria with fine small, rounded to somewhat transversely elongated areolae towards valve margins. Internally, areolae rows positioned between costae and each areola occluded with a hymen. In older material, hymenes often dissolved leaving unoccluded areolae. Type: –– Madebrökensee, Plön, Germany. Simonsen, 1987, fig. 194: 11, 12 (holotype). Observations:— According to Hustedt’s (1930) original description, this taxon has broadly rounded to elliptical valves with a valve length range between 9–15 µm, width range, 7–13 µm and stria density of 24 in 10 µm. In an investigation of Hustedt’s type material (Mal/97; Madebrökensee, Plön, Germany) Antoniades et al. (2009) found one valve in SEM matching the Holotype specimen designated by Hustedt. Cavinula vincentii Antoniades & Hamilton is distinguished from C. pseudoscutiformis by its more elliptic valve and the presence of an elongated pore-like fissure at both valve ends (not “s-shaped as in C. pseudoscutiformis).Valves reported by Snoeijs & Potapova (1995) from Zelenogorsk, Gulf of Finland, Russia, e.g. Length = 10–18 µm with an intermediate length of 13.7 µm and width = 8–14 µm, with an intermediate width of 10.7 appear to belong to C. vincentii. Cavinula scutiformis Grunow is distinguished by its larger valve size, more linearelliptical shape, denser striae, denser areolae and the differentiation of linear areolae along the axial area (see Krammer & Lange-Bertalot 1986, fig. 59: 10, 11). Cavinula pseudoscutiformis sensu stricto weakly resembles Navicula rotunda Hustedt (= Eolimna rotunda (Hustedt) Lange-Bertalot et al., see Levkov et al. 2007, fig. 66:1–13, fig. 67: 1–2) and Cavinula mollicula (Hustedt) Lange-Bertalot (sensu Lange-Bertalot & Metzeltin 1996, fig. 114: 5). C. pseudoscutiformis can be differentiated by the more spherical valve outline, the morphology of the raphe, mid-range stria density (not 20/10 µm or 32/10 µm), lower areola density and termination of the oppositely curved distal raphe ends on the valve face. Krammer & Lange-Bertalot (1986) reported a higher range of valve dimensions for C. pseudoscutiformis (L = 3.25–25 µm, W = 3–17 µm) and stria density between 20 and 26 in 10 µm. According to their description, C. pseudoscutiformis is a cosmopolitan taxon, present in North America, North and Eastern Europe, more often found in oligo to β-mesosaprobic waters. In the Canadian Archipelago, Antoniades et al. (2008) document valves with lengths between 8–18 µm, width 7–11 µm, stria density between 21–26 µm in 10 µm and 25–32 areolae in 10 µm. Morphological variability:–– During our observations we found three morphotypes of C. pseudoscutiformis. The first observed valve-group resembles the specimens with an elliptical valve outline and the following features: valve length 7.5–17 µm, width 5.5–14 µm, number of striae 20–22 in 10 µm (Figs 44–53). The second valve-group has a rounded valve outline with lanceolate axial area, punctate striae and the following features: valve length 4.5–12 (15) µm, width 4–10.5 (13) µm and number of striae 18–22 in 10 µm (Figs 54–58). During this study the same group characteristics observed from different provinces in Canada, were also found further south at Kernville, California, USA (Figs 59–63). The third valve-group contains specimens found in Nunavut, The Northwest Territories and Ontario, Canada (Figs 64–73). Valves have a rounded outline with broadly rounded ends, narrow linear axial area and a higher areola density. Valve length 5–9 µm and width 5–9 µm. Striae strongly radiate throughout the valve length, 20–22/10 µm. Axial area narrow, linear, not transforming into a defined central area. Raphe linear, filiform, the proximal and the distal raphe endings slightly deflected on the same side. The silica ridge that encircles the raphe in the previous valvegroup seems to be absent in the specimens belonging to this group. Based on these findings and the additional SEM observation of the different valve-groups, it is remarkable that although the first two groups exhibit a slight difference only in the valve outline, this character is not sufficient to separate the populations into different taxa. However, since the third valve-group differs in the valve outline, the morphology of the axial area, central area and the morphology of the raphe, we here suggest that these specimens represent a different morphotype of C. pseudoscutiformis. Distribution:— In the CANA collection, 189 localities for C. pseudoscutiformis have been identified across the Canada (excluding the provinces of Saskatchewan, Manitoba). C. pseudoscutiformis in Canada was low in abundance, typically lower than 5%, except at three localities: Baffin Island (9 %), Ellesmere Island (35%) and Ellef Ringnes Island (18%), all in the Arctic Archipelago. In the United States, C. pseudoscutiformis was verified across the north from Montana to Cape Cod and in the south from Florida to California. This taxon never exceeded 2.5% abundance from USA sites. In the CANA collection, its presence was confirmed in the states of New York, Florida and Massachusetts, but with abundances lower than 1.5 %. In the ANSP diatom collection, C. pseudoscutiformis was verified in the states of California and Georgia. However, a more detailed investigation is needed to verify the exact distribution of this taxon across the United States. C. pseudoscutiformis has a wide tolerance range for pH (6.3–8.0) and specific conductance (13–212 μS/cm), although preferring a more limited range of 6.5–7.1 in pH (Antoniades et al. 2008; Camburn & Charles 2000, Siver et al. 2005). This is an oligotrophic to weakly mesotrophic taxon occurring across central and northern North America (TP optima 8–12 μg/L) and prefers a moderate range in DOC (1.2–3.0 mg/L). For example, Caballero-Miranda (1996), reported C. pseudoscutiformis to be the most abundant taxon in the diatom assemblages from Lago del Sol, an acidic lake located in Nevado de Toluca (4 620 m asl.), Central Mexico and reported the following physical-chemical characteristics of the lake: pH=5.9, electric conductivity = 24.6 µS/cm, and total dissolved solids of 21.5 mg /L. Distribution Records:— Simonsen (1987, pg. 120, fig. 194: 11–12 = holotype, Germany), Antoniades et al. (2009, fig. 50: 5, 6; fig. 107: 1–3, Arctic Archipelago), Siver et al. (2005, fig. 38: 6–10, Massachusetts), Loseva (1982, fig. 66: 4a, 7a, 7b, Russia), Krammer & Lange-Bertalot (1986, fig. 457; fig. 8: 8, Europe), Metzeltin & Lange-Bertalot (1998, fig. 96: 6–9, Venezuela), Metzeltin & Witkowski (1996, fig. 2: 45, 46, Bear Island, Svalbard), Foged (1977, 26: 12, Ireland), Foged (1979, fig 30: 29, New Zealand), Foged (1981, fig. 30: 15, 16, Alaska), Watanabe (2005, fig. II B3 -18: 10–15, Japan), Potapova (2014, fig. 213, Bering Island, Kamchatka Peninsula, Russia)., Published as part of Cvetkoska, Aleksandra, Levkov, Zlatko, Hamilton, Paul B. & Potapova, Marina, 2014, The biogeographic distribution of Cavinula (Bacillariophyceae) in North America with the descriptions of two new species, pp. 181-207 in Phytotaxa 184 (4) on pages 192-195, DOI: 10.11646/phytotaxa.184.4.1, http://zenodo.org/record/5146714, {"references":["Hustedt, F. (1930) Bacillariophyta. In: Pascher, A. (Ed.) Gustav Fischer, Jena Die Susswasserflora Mitteleuropas 10: 1 - 466.","Simonsen, R. (1987) Atlas and catalogue of the diatom types of Friedrich Hustedt, vol. l - 3. J. Cramer, Stuttgart, Germany, 525 pp, 772 pls.","Antoniades, D., Hamilton, P. B., Hinz, F., Douglas, M. S. V., Smol, J. P. (2009) Eight new species of freshwater diatoms (Bacillariophyceae) from the Canadian Arctic Archipelago. Nova Hedwigia 88: 57 - 80. http: // dx. doi. org / 10.1127 / 0029 - 5035 / 2009 / 0088 - 0057","Snoeijs, P. & Potapova, M. (1995) Intercalibration and distribution of diatom species in the Baltic Sea, 3. Opulus Press, Uppsala. The Baltic Marine Biologists Publication 16 c, 125 pp.","Krammer, K. & Lange-Bertalot, H. (1986) Bacillariophyceae, 1. Teil: Naviculaceae. In: Ettl, H., Gerloff, J., Heynig, H. & Mollenhauer, D. (Eds.) Gustav Fischer, Stuttgart. Susswasserflora von Mitteleuropa (begrundet von A. Pascher) 2 / 1: 876 pp.","Levkov, Z., Krstic, S., Metzeltin, D. & Nakov, T. (2007) Diatoms of Lakes Prespa and Ohrid. About 500 taxa from ancient lake system. Iconographia Diatomologica 16: 603.","Lange-Bertalot, H. & Metzeltin, D. (1996) Indicators of oligotrophy, 800 taxa representative of three ecologically distinct lake types: Carbon buffered - oligodystrophic - weakly buffered soft water. Iconographia Diatomologica 2: 390.","Antoniades, D., Hamilton, P. B., Douglas, M. S. V. & Smol, J. P. (2008) Diatoms of North America: The freshwater floras of Prince Patrick, Ellef Ringnes and northern Ellesmere Islands from the Canadian Arctic Archipelago. Iconographia Diatomologica 17: 649.","Camburn, K. E. & Charles, D. F. (2000) Diatoms of low-alkalinity lakes in the northeastern United States. Special Publication 18. The Academy of Natural Sciences of Philadelphia, Scientific Publications, Philadelphia, 152 pp.","Siver, P. A., Hamilton, P. B., Stachura-Suchoples, K. & Kociolek, J. P. (2005) Diatoms of North America, the freshwater flora of Cape Cod, Massachusetts, U. S. A. Iconographia Diatomologica 14, 463 pp. http: // dx. doi. org / 10.1007 / s 10933 - 006 - 9041 - 6","Loseva, E. I. (1982) Atlas pozdnepliotsenovȳkh diatomei prikam'ya [= Atlas of late Pliocene diatoms of the Kama region], International Union for Quaternary Research. Congress 1982, Moscow (Institut geologii (Akademiia nauk SSSR. Komi nauchnyi tsentr), Moskva.","Metzeltin, D. & Lange-Bertalot, H. (1998) Tropical diatoms of South America. I. About 700 predominantly rarely known or new taxa representative of the neotropical flora. Iconographia Diatomologica 5: 695.","Metzeltin, D. & Witkowski, A. (1996) Diatomeen der Baren-Insel. Iconographia Diatomologica 4: 232.","Foged, N. (1977) The diatoms in four postglacial deposits at Godthabsfjord, West Greenland. Meddelelser om GrOnland 199: 1 - 64, 8 pls.","Foged, N. (1979) Diatoms in New Zealand, the North Island. Bibliotheca Phycologica 47: 1 - 225.","Watanabe, T., Ohtsuka, T., Tuji, A., Houki, A. (2005) Picture book and ecology of the freshwater diatoms. Uchida-rokakuho, Tokyo, 666 pp.","Potapova, M. (2014) Diatoms of Bering Island, Kamchatka, Russia. Nova Hedwigia 143: 63 - 102."]}

Cavinula vincentii Antoniades & Hamilton (Figs 74–81, 172–180) Valves elliptic with broadly rounded ends. Valve length 11–13.5 µm, width 8–10 µm. Striae radiate at center, more strongly radiate towards ends, 22–26 in 10 µm. Striae uniseriate with elliptical to rounded areolae discernable in LM. Axial area narrow, linear; central area small, elliptical or almost round, to asymmetrically elongated. Short and long alternating striae surround the central area. Short striae along valve length, extend onto valve mantle. Internally striae between thickened costae and areolae covered with a hymen. Externally, raphe filiform. Proximal raphe fissures expanded pores, slightly unilaterally bent; distal raphe fissures small pores, terminating on valve face. Internally, raphe linear, positioned on thickened sternum. Terminal raphe fissures with a helictoglossa, not present on proximal raphe ends. Adjacent to distal raphe ends one enlarged, transversally elongated pore-like fissure, externally separated with a small ridge-like structure from areolae. Copulae open bands, with one row of pores, two or more at each valve. Type: –– White Pond, Alert, Ellesmere Island, Nunavut, Canada. Antoniades et al. 2009, figs 7–9 (holotype). Here presented in Figs 172–180 (type material). Observations:— Cavinula vincentii was described from Ellesmere Island, Canada. The taxon resembles the elliptical forms of C. pseudoscutiformis (Figs 44–53), but it is clearly distinguished by the valve outline, which is more elliptical, has a larger central area and the general morphology of the raphe. The main morphological character which separates C. vincentii from C. pseudoscutiformis and also the other taxa belonging to the genus Cavinula is the presence of the pore-like fissures at the valve apices. Based on SEM photomicrographs one other taxon, C. scutiformis has distinct pore-like fissures at the valve apices. Additionally, a specimen identified by (Krammer & Lange-Bertalot, 1986, fig. 59: 12) as C. pseudoscutiformis from Europe appears to be similar to C. vincentii, but a more detailed LM and SEM observation is necessary to confirm this. Distribution:— Antoniades et al. (2009) described C. vincentii from the locality White Pond, Alert, Ellesmere Island, Nunavut, a shallow pond with inorganic sediments and high pH (8.3). During our observation of a number of slides deposited at the CANA Diatom Collection, the presence of C. vincentii was confirmed in the following localities: two sediment cores recovered from the deepest part of Lake Oakley and Little Clear Lake, respectively, both lakes located in the province of Ontario. This taxon was also observed in the recent samples from Lake Abitibi (Québec), Lake Contwoyto (Northwest Territories) and in samples originating from Isachsen (Ellef Ringnes Island, Nunavut Territory). Additionally, C. vincentii was confirmed from one samples collected in Pennsylvania (Fig. 77). This taxon is present in mildly acidic to circumneutral, oligotrophic waters across northern North America. Distribution Records:— Antoniades et al. (2009, figs 7–9, 12, 13, 60–64, Arctic Archipelago).

Cavinula davisiae Bahls (Figs 93–98) Valves lanceolate to lanceolate-elliptic, with rounded apices. Valve length 14–31 µm, width 7.5–10 µm. Striae composed of round to elliptic areolae, 32–36 in 10 µm. Areolae around central area elongated; internally covered with hymenes. Stria density 24–26 in 10 µm. Striae radiate throughout. Central area broadly rounded and formed by alternating long and short striae along both valve margins. Axial area narrow and linear, internally axial area thickened, along raphe terminating prior to central area. Externally, raphe filiform, proximal raphe fissures tear-drop in shape and distal fissures hooked to opposite sides on valve face. Internally, proximal fissures terminate as simple pores, terminal fissures end in helictoglossae. Type:— Clover Lake, Mount Rainier National Park, Pierce County, Washington, USA; Bahls 2013, fig. 48 (holotype). Here presented in Figs 93–98 from isotype slide ANSP GC65165. Observations:— On initial observation, this taxon is similar to C. cocconeiformis, C. variostriata (Krasske) Mann and C. lapidosa (Krasske) Lange-Bertalot. Cavinula davisiae is differentiated by a lower stria density and more pronounced central area; it is further differentiated from C. variostriata (Lange-Bertalot et al. 1996, fig. 19: 27–30) by the smaller central area and the lanceolate not linear valve. In addition, C. lapidosa has a linear valve outline and panduriforme shape of the central area (Lange-Bertalot et al. 1996, fig. 19: 22–26). Distribution:— Cavinula davisiae is found across western northern North America and common in circumneutral waters with low conductivity. Previously, specimens were identified under Navicula variostriata Krasske. Validated identifications for this taxon are from Adak Island, Alaska (Hein 1990, originally as C. variostriata) and coastal British Columbia (Pienitz et al. 2003, originally as C. cf. variostriata). Distribution Records:— Bahls, L. (2013, fig. 15: 43–51, fig. 15: 48= holotype, Washington)., Published as part of Cvetkoska, Aleksandra, Levkov, Zlatko, Hamilton, Paul B. & Potapova, Marina, 2014, The biogeographic distribution of Cavinula (Bacillariophyceae) in North America with the descriptions of two new species, pp. 181-207 in Phytotaxa 184 (4) on page 187, DOI: 10.11646/phytotaxa.184.4.1, http://zenodo.org/record/5146714, {"references":["Bahls, L. (2013) New diatoms (Bacillariophyta) from western North America. Phytotaxa 82: 7 - 28. http: // dx. doi. org / 10.11646 / phytotaxa. 82.1.2","Hein, M. (1990) Flora of Adak Island, Alaska: Bacillariophyceae (Diatoms). Bibliotheca Diatomologica 21: 133.","Pienitz, R., Fedje, D. & Poulin, M. (2003) Marine and Non-Marine Diatoms from the Haida Gwaii Archipelago and Surrounding Coasts, Northeastern Pacific, Canada. Bibliotheca Diatomologica 48: 146."]}

Psammothidium alpinum Potapova & Enache sp. nov. (Figs 9���21, 40���44) Valvae linearae ellipticae, ovalis, 6.3���9.1 ��m latae, 14.6���30 ��m longae. Raphovalva cum area axialis angusta linearis versus, area centralis rectagularis. Raphe recta poris centralibus unciformis, termini distale punctiformis. Araphovalva cum area axialis angusta, area centralis circularis, irregularis, 1/2 valvae lata. Striae transapicales paulo radiatae, 22���25 in 10 ��m cum striae breviores intercalares. Areolae rotundae, grossae, 25 in 10 ��m. Valves linear-elliptic to oval, 6.3���9.1 ��m wide, 14.6���30 ��m long. Raphe valve with narrow linear axial area and rectangular-irregular central area. Raphe straight with hook-like proximal pores, drop-shaped distal endings (Figs 10, 11, 13, 15, 16, 20). Rapheless valve with narrow axial area, irregular, rounded central area, occupying about �� of valve breadth (Figs 9, 12, 14, 17���19, 21). Transapical striae slightly radiate, 22���25 in 10 ��m, with shortened marginal striae present (figs 41, 43). Areolae coarse, round, 25 in 10 ��m (Fig. 44). Type:��� USA. Washington: Cascade Mountains, Snow Lake, 46.7576�� N, 121.6982468�� W, lake sediment (2���2.5-cm depth core interval; lake maximum depth 9.75 m), collected 07 October 2009, collection WACA019, (Circled specimen (Figs 9, 10) on slide GC64862, accession # GC64862 (ANSP!), holotype, designated here; circled specimens on slide GC64863 (ANSP!) and slide 84223 (CANA!), isotypes, designated here). Etymology: ���specific epithet refers to the occurrence of the new species in alpine, high elevation lakes. Psammothidium alpinum is similar to P. bioretii (Germain 1957: 85) Bukhtiyarova et Round (1996: 9) in valve size and possession of relatively coarse areolae. It differs from P. bioretii by having more elongate, linear-elliptical valve shape with nearly parallel sides, and a straight central sternum (versus diagonal in P. bioretii). In SEM (Figs 40���44), P. alpinum displays a characteristic doublet of smaller areolae at the valve/ mantle junction and around the mantle (Figs 40, 42). On raphe valves, the central area nearly reaches the valve margin and is bounded by 4���8 short striae. The raphe has characteristic hook-like widely spaced proximal endings (Fig 40) that deflect in the same direction externally (Fig. 40) and opposite internally (Fig. 41). While P. bioretii has terminal raphe fissures curved to opposite sides, P. alpinum lacks terminal fissures, and distal external raphe endings are drop-shaped and do not expand beyond the last stria (Fig. 41). Similar to P. bioretii, P. alpinum has coarse, round areolae visible in LM; a row of coarser areolae border the sternum and central area in LM (Figs 10, 11) and a double row of finer areolae bordering the valve face-mantle junction is visible in SEM (Figs 40, 42). Short intercalary striae are present along the valve margin and expand on the mantle (Figs 41, 43). Psammothidium alpinum has similar valve shape as P. chlidanos (Hohn et Hellerman 1963: 273) Lange-Bertalot (1999: 285) but it can be easily distinguished by its coarser striae and areolae visible in LM. P. alpinum was present in Hidden Lake NOCA (bottom sample, 2% relative abundance) and very rare in top samples from Snow and Stiletto lakes., Published as part of Enache, Mihaela D., Potapova, Marina, Sheibley, Rich & Moran, Patrick, 2013, Three new Psammothidium species from lakes of Olympic and Cascade Mountains in Washington State, USA, pp. 49-57 in Phytotaxa 127 (1) on page 53, DOI: 10.11646/phytotaxa.127.1.8, http://zenodo.org/record/5085461, {"references":["Germain, H. (1957) Achnanthes bioreti n. sp., diatomee nouvelle. Bulletin de la Societe Botanique de France 104 (suppl.): 85 - 86.","Bukhtiyarova, L. & Round, F. E. (1996) Revision of the genus Achnanthes sensu lato section Marginulatae Bukht. Sect. nov. of Achnanthidium Kutz. Diatom Research 11: 1 - 30. http: // dx. doi. org / 10.1080 / 0269249 X. 1996.9705361","Hohn, M. H. & Hellerman, J. (1963) Taxonomy and structure of diatom populations from three eastern North American rivers. Transactions of the American Microscopical Society 82: 250 - 329. http: // dx. doi. org / 10.2307 / 3223932","Lange-Bertalot, H. (1999) Neue Kombinationen von Taxa aus Achnanthes Bory (sensu lato). Iconographia Diatomologica 6: 276 - 289."]}

Psammothidium lacustre Enache & Potapova sp. nov. (Figs 1���8, 35���39) Valvae lanceolate, 8.4���11.2 ��m latae, 16.7���28 ��m longae. Raphovalva cum area axialis linearis versus centro expanso, area centralis rectangularis, �� vel 2/3 valvae lata. Raphe recta poris centralibus simples cum cristae et sulci, interne paulo curvatae. Fissuris terminalibus simplex, longae, ad versum curvatae. Araphovalva cum area axialis angusta, area centralis circulare, 2/3 valvae lata. Striae transapicales radiatae 22���26 in 10 ��m; areolae cum foramina externae circulares, foramina internae transapicalem elongatae, 40���60 in 10 ��m. Valves lanceolate, 8.4���11.2 ��m wide, 16.7���28 ��m long. Raphe valve with linear axial area, rectangular central area, occupying �� to 2/3 of valve breadth (Figs 2, 3, 6, 7). Proximal raphe endings slightly deflected internally (Fig. 36). Terminal raphe fissures simple, long, deflected in opposite directions (Figs 2, 3, 6). Rapheless valve with narrow axial area, round central area occupying 2/3 of the valve breadth (Figs 1, 4, 5, 8). Striae radiate, 22���26 in 10 ��m; areolae 40���60 in 10 ��m, with round external foramina, and internal openings elongated transapically on both valves (Figs 35���39). Type:��� USA. Washington: Cascade Mountains, Snow Lake, 46.7576�� N, 121.6982468�� W, lake sediment (2���2.5-cm depth core interval; lake maximum depth 9.75 m), collected 07 October 2009, collection WACA019, (Circled specimen (Figs 1, 2) on slide GC64860, accession # GC64860 (ANSP!), holotype, designated here; circled specimens on slide GC64861 (ANSP!) and slide 84222 (CANA!), isotypes, designated here). Etymology:���specific epithet refers to the occurrence of the new species in a lacustrine environment. The species with the closest morphological features to Psammothidium lacustre is P. helveticum (Figs 32��� 34). Psammothidium lacustre has much larger size, with valve width greather than 8 ��m, and more acute valve ends compared to P. helveticum. SEM investigations (Figs 35���39) revealed that the proximal raphe endings are internally slightly deflected in opposite directions (Fig. 36), similarly to P. helveticum (see Bukhtiyarova & Round 1996, figure 23). The striae extend uninterrupted onto the mantle, and short striae are present near the central area and occasionally in other parts of valve margin (Fig. 38). Areolae have round external foramina and transapically elongated internal openings (Figs 37, 39). The shape of the axial and central areas on rapheless valves is similar in Psammothidium lacustre and P. helveticum, except that the central area is narrower in P. helveticum. Internally, the shape of areolae is also different: elongated with rims and grooves in P. lacustre versus round or rectangular in P. helveticum (see Bukhtiyarova & Round 1996, figure 23). In LM, P. lacustre is relatively easy to separate from P. helveticum; P. lacustre is larger, has more lanceolate shape, and coarser striae (22���24 versus 23���28) and areolae. Psammothidium lacustre was rare in study lakes (, Published as part of Enache, Mihaela D., Potapova, Marina, Sheibley, Rich & Moran, Patrick, 2013, Three new Psammothidium species from lakes of Olympic and Cascade Mountains in Washington State, USA, pp. 49-57 in Phytotaxa 127 (1) on pages 51-53, DOI: 10.11646/phytotaxa.127.1.8, http://zenodo.org/record/5085461, {"references":["Bukhtiyarova, L. & Round, F. E. (1996) Revision of the genus Achnanthes sensu lato section Marginulatae Bukht. Sect. nov. of Achnanthidium Kutz. Diatom Research 11: 1 - 30. http: // dx. doi. org / 10.1080 / 0269249 X. 1996.9705361"]}

Psammothidium nivale Potapova & Enache sp. nov. (Figs 22���31, 45���48) Valvae ellipticae, 5.6���6 ��m latae, 11.7���15 ��m longae. Raphovalva cum area axialis linearis, area centralis transapicalem rectagularis vel ovalis, 2/3 valvae lata. Raphe recta cum poris proximales paene expansae, in sulci, cum terminis distales simplices. Araphovalva cum area axialis ad apicem angusta, versus centro expansa, rhombico-lanceolata, 2/3 valvae lata. Striae transapicales paulo radiatae, 26���28 in 10 ��m in araphovalva, 30���32 in 10 ��m in raphovalva. Valves elliptical, 5.6���6 ��m wide and 11.7���15 ��m long. Raphe valve with linear axial area, central area transapically rectangular to oval occupying 2/3 of the valve breadth. Raphe with proximal pores slightly expanded, located in grooves, and with simple distal endings (Figs 23, 25, 27, 28). Rapheless valve with axial area narrow at apices and widening towards valve centre in a rhombic-lanceolate shape, occupying 2/3 of the valve breadth (Figs 22, 24, 26, 29, 30). Striae slightly radiate, 26���28 in 10 ��m on rapheless valve, 30���32 on raphe valve. Type:��� USA. Washington: Cascade Mountains, Snow Lake, 46.7576�� N, 121.6982468�� W, lake sediment (2���2.5-cm depth core interval; lake maximum depth 9.75 m), collected 07 October 2009, collection WACA019, (Circled specimen (Figs 22, 23) on slide GC64864, accession # GC64864 (ANSP!), holotype, designated here; circled specimens on slide GC64865 (ANSP!) and slide 84224 (CANA!), isotypes, designated here). Etymology:���specific epithet refers to the name of the lake (Snow Lake) from where the species was found and described. Psammothidium nivale is distinguished from other Psammothidium species by characteristic coarser striae and areolae on rapheless valve compared to raphe valve. The linear axial area on raphe valves widens slightly near the valve center, and the transapically rectangular to oval central area is bounded by 4���5 shortened striae. External proximal raphe endings are located in grooves, which gradually widen toward valve center. External distal raphe endings are drop-shaped and do not extend beyond the last stria (Fig. 45). Characteristic coarse areolae on rapheless valves have the appearance of transapically elongated slits in SEM (Figs 47���48). In the SEM, the shape of the areolae���transapically elongate���resemble those of P. subatomoides in SEM. However, P. nivale is distinguished from the latter species by all other valve characteristics: more elongated shape of the valve and larger size, shape of central area on both raphe and rapheless valve and clear dimorphism of raphe and rapheless valve in striae density and areolae size. P.nivale was found in Snow Lake and Hidden Lake NOCA in very low abundance (, Published as part of Enache, Mihaela D., Potapova, Marina, Sheibley, Rich & Moran, Patrick, 2013, Three new Psammothidium species from lakes of Olympic and Cascade Mountains in Washington State, USA, pp. 49-57 in Phytotaxa 127 (1) on page 54, DOI: 10.11646/phytotaxa.127.1.8, http://zenodo.org/record/5085461