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During our investigations on the freshwater diatoms from Qinghai Province, China, four sympatric Surirella taxa belonging to the group Pinnatae were analysed. Based on morphological observations derived from light and scanning electron microscopy, three of these four taxa were identified as: S. minuta, S. lacrimula, and S. brebissonii var. kuetzingii. The fourth taxon is described as Surirella liubingii sp. nov., a new species with a unique combination of characteristics. These include the distribution pattern of its costa-stria bundles (CSBs) alternating with its over-fibula costae (OFCs), which is formed by the distinctly elevated CSBs on the valve face, mostly composed of three costae, and OFCs with a remarkedly lower position. Other characteristics include the presence of robust fibulae extending to the valve midline, the presence of only one portula between two adjacent fibulae, and a “pseudoseptum” extending internally from the valve margin. From the observations on these four Surirella taxa, we described and discussed two types of fibula (one in which the fibula nearly reaches the valve midline and one with short fibula) and two types of portula morphology (one with only one portula between two adjacent fibulae and the other with 2–4 portulae between two adjacent fibulae).

Surirella brebissonii var. kuetzingii Krammer & Lange-Bertalot 1987 (LM: Figs 78–89, SEM: Figs 90–101, 106) Observations:— LM: Valve outline ovate to elliptical with broadly rounded headpole and narrowly rounded footpole. Valve dimensions (n = 25): 14–25 μm long, 6.9–8.8 μm wide (measured at widest part of the valve), length/width ratio 1.4–1.6. Valve composed of two portions: central portion and outside portion (indicated in Fig. 83). Costa-stria bundles (CSBs) visible, alternated with over-fibula costae (OFCs) from pole to pole. CSBs reaching valve margins. CSBs parallel at valve middle part, radiate approaching apices. Fibulae well-developed, spanning c. 1/4 of valve width, not extending to midline, 6–8 in 10 μm. SEM: Each CSB often composed of three costae and four striae (Figs 90–92). Striae multiseriate, composed of 3–5 rows of areolae, 23–25 in 10 μm (measured from SEM images, n = 4). Outside openings of areolae slit-like (Figs 92–95). Raphe canal located directly on mantle. Distal raphe endings simple and interrupting at both apices (Figs 93, 94, two arrows respectively). Internally, valve composed of two portions: central portion and outside portion (indicated in Fig. 97). Wall of raphe canal growing slightly into cell cavity leaving the portulae visible. Fibulae short, spanning c. 1/4 of valve width, not extending to valve midline (Figs 96–98). Raphe continuous at headpole (Fig. 99, wavy arrow), but interrupted at footpole (Fig. 100, two arrows). Three portulae produced between two adjacent fibulae (Figs 101, 106, three arrows). The areas between the fibulae form marginal trough-like depressions (Fig. 106). Ecology and distribution:— Epilithic in freshwater river. Surirella brebissonii var. kuetzingi was found in the same sampling site with S. liubingii, for the environmental parameters, see above. It is commonly found in Europe with reports from Germany, France and Poland (Krammer & Lange-Bertalot 1987, Bey & Ector 2013, Szczepocka et al. 2018).

Surirella lacrimula J.D. English 2012 (LM: Figs 55–66, SEM: Figs 67–77, 105) Observations:— LM: Valve outline ovate with broadly rounded headpole and cuneate footpole (Figs 55–66). Valve dimensions (n = 30): length 24–34 μm, width 10.3–13.1 μm (measured at the widest part of the valve), length/width ratio 2.1–2.6. Valve composed of two distinct portions: central portion and outside portion (indicated in Fig. 59). Fibulae evident, spanning c. 1/4 of valve width, not extending to midline, 7–9 in 10 μm. Fibulae parallel at valve middle, radiate approaching apices. SEM: Valve face flat making CSBs difficult to distinguish as CSBs not elevated from OFCs (Fig. 67–71). Striae multiseriate, composed of 3 or 4 rows of areolae, 30–32 in 10 μm (measured from SEM images, n = 4). Outside openings of areolae slit-like (Figs 68–71). Raphe canal located directly on mantle. Internally, valve composed of two portions: central portion and outside portion (indicated in Fig. 74). Wall of raphe canal growing slightly into cell cavity so that the portulae are easily visible (Figs 72–74). Fibulae short, a few bifurcate, spanning c. 1/4 of valve width, not extending to valve midline (Figs 72–74). Raphe continuous at headpole (Fig. 76, wavy arrow), but interrupted at footpole (Fig. 77, two arrows). One to three portulae occurring between two adjacent fibulae (Fig. 75, three arrows; Fig. 105, three arrows). Distribution:— S. lacrimula was found in the same site with S. liubingii. From the literature, this species appears to have a global distribution as it has been reported in the USA, France, Argentina, and Iran (English & Potapova 2012, Bey & Ector 2013, Seeligmann & Maidana 2019, Safiallah et al. 2020)., Published as part of Long, Ji-Yan, Liu, Bing, Rioual, Patrick, Yang, Bin & Zhou, Min, 2023, Ultrastructure of four Surirella taxa (Bacillariophyceae) from Qinghai Province, northwest China, with reference to the characteristics of portulae, pp. 163-177 in Phytotaxa 592 (2) on page 168, DOI: 10.11646/phytotaxa.592.2.11, http://zenodo.org/record/7840352, {"references":["English, J. D. & Potapova, M. G. (2012) Ontogenetic and interspecific valve shape variation in the Pinnatae group of the genus Surirella and the description of S. lacrimula sp. nov. Diatom Research 27 (1): 9 - 27. https: // doi. org / 10.1080 / 0269249 X. 2011.642950","Bey, M. - Y. & Ector, L. (2013) Atlas des diatomees des cours d'eau de la region Rhone-Alpes, Tome 6. Bacillariacees, Rhopalodiacees, Surirellacees. DREAL Rhone-Alpes, Lyon, France, pp. 973 - 1182.","Seeligmann, C. & Maidana, N. (2019) Diatomeas perifiticas de un rio de montana (Tucuman, Argentina). Lilloa 56 (1): 64 - 91. https: // doi. org / 10.30550 / j. lil / 2019.56.1 / 5","Safiallah, S., Saadatmand, S., Kheiri, S. & Iranbakhsh, A. (2020) Biodiversity of diatoms in the Kashkan River in the Zagros Mountains, western Iran. The Iranian Journal of Botany 26 (2): 141 - 161. https: // doi. org / 10.22092 / ijb. 2020.351698.1296"]}

Surirella liubingii J.Y.Long sp. nov. (LM: Figs 1–14, SEM: Figs 15–26, 102, 103) Observations:— LM: Valve outline long-ovate to ovate with broadly rounded headpole and cuneate footpole (Figs 1– 14). Valve dimensions (n = 21): length 22–33 μm, width 8.5–9.9 μm (measured at widest part of the valve), length/width ratio 2.3–3.7. Costa-stria bundles (CSBs) distinct, alternated with over-fibula costae (OFCs) from pole to pole. CSBs not reaching valve margins because the internal wall of raphe canal growing into cell cavity to form a “pseudoseptum” from the valve margin (indicated by two arrows in Fig. 4, see also Figs 21–23). CSBs parallel at the valve middle, slightly radiate approaching apices. Fibulae distinct, extending to midline, 6–7 in 10 μm. SEM: Each CSB mostly composed of three costae and four striae, but occasionally two costae and three striae or four costae and five striae (Figs 15–17). Tiny rib-like thickenings produced externally (Fig. 18, arrows). Striae multiseriate, composed of 3 or 4 rows of areolae, 24–26 in 10 μm (measured from SEM images, n = 3). Outside openings of areolae round to slit-like (Figs 18–20). Raphe canal located directly on mantle. Distal raphe endings simple and interrupting at both apices (Figs 19, 20, two arrows respectively). Internally, wall of raphe canal growing into cell cavity to the extent that the internal raphe canal wall is developed to form a longitudinal siliceous plate (a “pseudoseptum” from the valve margin, indicated by two double-headed arrows in Fig. 21), which hides the portula structure. The wall of the raphe canal is striated (Fig. 26). Fibulae robust, occasionally bifurcate, extending to valve midline (Figs 21–23, 25, 102). Raphe continuous at headpole (Fig. 24, arrow), but interrupted at footpole (Fig. 26, two arrows). One portula produced between two adjacent fibulae (Fig. 103, three arrows). Type:— CHINA, Qinghai province, Menyuan County: unnamed freshwater river course, sampling point 37°27'28" N, 101°23'15" E, 2940 m asl. Bing Liu, 18 th July 2019 (holotype slide JIU! DIA202315, specimen circled on slide = Fig. 1). Etymology:— Named after Dr. Bing Liu who is the first author’s supervisor and who collected the samples. Ecology and distribution:— Epilithic in river. The following environmental parameters were measured. Conductivity was 448 ± 1 μS̔cm –1, pH was 8.36 ± 0.03 and water temperature was 11.9 ± 0.5 °C. So far, Surirella liubingii has only been found in the type locality., Published as part of Long, Ji-Yan, Liu, Bing, Rioual, Patrick, Yang, Bin & Zhou, Min, 2023, Ultrastructure of four Surirella taxa (Bacillariophyceae) from Qinghai Province, northwest China, with reference to the characteristics of portulae, pp. 163-177 in Phytotaxa 592 (2) on pages 166-167, DOI: 10.11646/phytotaxa.592.2.11, http://zenodo.org/record/7840352

Surirella minuta Brébisson in Kützing 1849 (LM: Figs 27–42, SEM: Figs 43–54, 104) Observations:— LM: Valve outline long-ovate to ovate with broadly rounded headpole and cuneate footpole (Figs 27–42). Valve dimensions (n = 38): length 20–46 μm, width 8.4–11.0 μm (measured at widest part of the valves), length/width ratio 2.1–4.4. Costa-stria bundles (CSBs) evident, alternated with over-fibula costae (OFCs) from pole to pole. CSBs reaching valve margins. CSBs parallel at valve middle, radiate approaching apices. Fibulae evident, nearly extending to midline, 7–9 in 10 μm. SEM: Each CSB mostly composed of three costae and four striae, or two costae and three striae (Figs 43–46). Striae multiseriate, composed of 3–5 rows of areolae, 25–27 in 10 μm (measured under SEM images, n = 3). Outside openings of areolae slit-like (Figs 45–48). Raphe canal located directly on mantle. Distal raphe endings simple and interrupting at both apices (Figs 47, 48, two arrows respectively). Internally, wall of raphe canal only slightly growing into cell cavity such as the portulae are visible (Figs 49, 50, 54, 104). Fibulae medium-sized, occasionally bifurcate, extending to valve midline (Figs 49–51). Each fibula corresponds to a sinking in the mantle (Fig. 51). Raphe continuous at headpole (Fig. 52, wavy arrow), but interrupted at footpole (Fig. 53, two arrows). One portula produced between two adjacent fibulae (Fig. 54, two arrows, Fig. 104, three arrows). Distribution:— Surirella minuta was commonly found and was dominant in the assemblages collected on the stone surfaces in the river course. It was associated with S. liubingii, S. lacrimula and S. brebissonii var. kuetzingi. From the literature, this species has a global distribution (Krammer & Lange-Bertalot 1987, English & Potapova 2012, Bey & Ector 2013, Dedić et al. 2015, Caglar et al. 2022)., Published as part of Long, Ji-Yan, Liu, Bing, Rioual, Patrick, Yang, Bin & Zhou, Min, 2023, Ultrastructure of four Surirella taxa (Bacillariophyceae) from Qinghai Province, northwest China, with reference to the characteristics of portulae, pp. 163-177 in Phytotaxa 592 (2) on page 168, DOI: 10.11646/phytotaxa.592.2.11, http://zenodo.org/record/7840352, {"references":["Kutzing, F. T. (1849) Species algarum. Lipsiae [Leipzig]: F. A. Brockhaus. pp. [i] - vi, [1] - 922.","Krammer, K. & Lange-Bertalot, H. (1987) Morphology and taxonomy of Surirella ovalis and related taxa. Diatom Research 2 (1): 77 - 95. https: // doi. org / 10.1080 / 0269249 X. 1987.9704986","English, J. D. & Potapova, M. G. (2012) Ontogenetic and interspecific valve shape variation in the Pinnatae group of the genus Surirella and the description of S. lacrimula sp. nov. Diatom Research 27 (1): 9 - 27. https: // doi. org / 10.1080 / 0269249 X. 2011.642950","Bey, M. - Y. & Ector, L. (2013) Atlas des diatomees des cours d'eau de la region Rhone-Alpes, Tome 6. Bacillariacees, Rhopalodiacees, Surirellacees. DREAL Rhone-Alpes, Lyon, France, pp. 973 - 1182.","Dedic, A., Plenkovic-Moraj, A., Kralj Borojevic, K. & Hafner, D. (2015) The first report on periphytic diatoms on artificial and natural substrate in the karstic spring Bunica, Bosnia and Herzegovina. Acta Botanica Croatica 74 (2): 393 - 406. https: // doi. org / 10.1515 / botcro- 2015 - 0029","Caglar, M., Bulut, H. & Selamoglu, Z. (2022) Epipsammic diatom fauna of Karabey Creek in Turkiye. Survey in Fisheries Sciences 9 (1): 65 - 77. https: // doi. org / 10.18331 / SFS 2022.9.1.6"]}

Surirella brebissonii var. kuetzingii Krammer & Lange-Bertalot 1987 (LM: Figs 78–89, SEM: Figs 90–101, 106) Observations:— LM: Valve outline ovate to elliptical with broadly rounded headpole and narrowly rounded footpole. Valve dimensions (n = 25): 14–25 μm long, 6.9–8.8 μm wide (measured at widest part of the valve), length/width ratio 1.4–1.6. Valve composed of two portions: central portion and outside portion (indicated in Fig. 83). Costa-stria bundles (CSBs) visible, alternated with over-fibula costae (OFCs) from pole to pole. CSBs reaching valve margins. CSBs parallel at valve middle part, radiate approaching apices. Fibulae well-developed, spanning c. 1/4 of valve width, not extending to midline, 6–8 in 10 μm. SEM: Each CSB often composed of three costae and four striae (Figs 90–92). Striae multiseriate, composed of 3–5 rows of areolae, 23–25 in 10 μm (measured from SEM images, n = 4). Outside openings of areolae slit-like (Figs 92–95). Raphe canal located directly on mantle. Distal raphe endings simple and interrupting at both apices (Figs 93, 94, two arrows respectively). Internally, valve composed of two portions: central portion and outside portion (indicated in Fig. 97). Wall of raphe canal growing slightly into cell cavity leaving the portulae visible. Fibulae short, spanning c. 1/4 of valve width, not extending to valve midline (Figs 96–98). Raphe continuous at headpole (Fig. 99, wavy arrow), but interrupted at footpole (Fig. 100, two arrows). Three portulae produced between two adjacent fibulae (Figs 101, 106, three arrows). The areas between the fibulae form marginal trough-like depressions (Fig. 106). Ecology and distribution:— Epilithic in freshwater river. Surirella brebissonii var. kuetzingi was found in the same sampling site with S. liubingii, for the environmental parameters, see above. It is commonly found in Europe with reports from Germany, France and Poland (Krammer & Lange-Bertalot 1987, Bey & Ector 2013, Szczepocka et al. 2018)., Published as part of Long, Ji-Yan, Liu, Bing, Rioual, Patrick, Yang, Bin & Zhou, Min, 2023, Ultrastructure of four Surirella taxa (Bacillariophyceae) from Qinghai Province, northwest China, with reference to the characteristics of portulae, pp. 163-177 in Phytotaxa 592 (2) on pages 168-170, DOI: 10.11646/phytotaxa.592.2.11, http://zenodo.org/record/7840352, {"references":["Krammer, K. & Lange-Bertalot, H. (1987) Morphology and taxonomy of Surirella ovalis and related taxa. Diatom Research 2 (1): 77 - 95. https: // doi. org / 10.1080 / 0269249 X. 1987.9704986","Bey, M. - Y. & Ector, L. (2013) Atlas des diatomees des cours d'eau de la region Rhone-Alpes, Tome 6. Bacillariacees, Rhopalodiacees, Surirellacees. DREAL Rhone-Alpes, Lyon, France, pp. 973 - 1182.","Szczepocka, E., Nowicka-Krawczyk, P. & Kruk, A. (2018) Deceptive ecological status of urban streams and rivers - evidence from diatom indices. Ecosphere 9 (7): e 02310. https: // doi. org / 10.1002 / ecs 2.2310"]}

Two new species in the genus Bacillaria, B. sinensis sp. nov. and B. dongtingensis sp. nov., are described from Dongting Lake, China. Both share the linear-lanceolate valve outline and the fault sites (i.e., branching and/or fusion of transapical ribs), the latter a character of the genus. Even though B. sinensis and B. dongtingensis are found at the same specific locality (sympatric), they differ by two characters: (1) the valves of B. sinensis have asymmetrical flanges on both sides of the raphe, while the raphe flange of B. dongtingensis is only on one side of the raphe; and (2) the valves of B. sinensis lack spines on the valve margins while B. dongtingensis has spines on both margins. Bacillaria sinensis and B. dongtingensis both possess two forms of fault sites on the same valves, i.e., they have both branching of transapical ribs and fusion of transapical ribs on the broader side of valve. This feature is not found in other species of Bacillaria, so it is unique. Bacillaria sinensis and B. dongtingensis are the first two species of Bacillaria reported from a typical and ‘normal’ freshwater habitat.

Bacillaria sinensis Bing Liu & D.M. Williams sp. nov. (Figs 1���29) LM: Valves linear-lanceolate, often with slightly swollen central margins (e.g. Figs 1���9), tapering to cuneate or rostrate apices (Figs 1���11). Valve dimensions (n = 40): 52���84 ��m long, 4.6���5.6 ��m wide. Fibulae distinct, situated approximately along valve midline, unevenly spaced, 7���12 in 10 ��m. Striae indistinct, parallel throughout valve, 27���29 in 10 ��m. Fault sites on valve broader side difficult to discern using LM. SEM: Colony and frustule view: Cell to cell attachment forms colony (Figs 12, 13). Frustule composed of (probably) five open girdle bands (Figs 14���17, labeled B1 to B5), four associated with the epivalve, only one is seen with the hypovalve (Figs 16, 17). Pars exterior deeper than pars interior, stepped, two rows of poroids located in pars exterior along midline, except near each apex becoming one row (Figs 15, 16, arrow, 17). Poroids of valvocopula covered externally by hymenes (Figs 15���17). Valve view: Valve linear-lanceolate, with slightly swollen central margins (Figs 18, 24). Raphe nearly central, continuous from pole to pole, distal raphe endings T-shaped (���tongue-in-groove��� structure); two raphe flanges present on each side of raphe, asymmetrical due to raphe flange on narrower valve side more developed than that on broader side, terminating before reaching poles (Figs 14���23). Transapical ribs originate with raphe ribs, parallel; striae uniseriate, composed of rounded areolae covered by hymenes externally, continuing onto mantle. Marginal spines absent. On broader side of valve, one transapical rib forming two branches at some sites (Figs 19, 21, 25, 28, 29, arrow, respectively), or two merging into one occasionally (Figs 15, curved arrow; 19, 22, 23, 29, three curved arrows, respectively). Fibulae rib-like, arching into cell (Figs 24���29). Two fibular ribs asymmetrical, i.e. fibular rib on broader side of valve more developed than that on narrower side (Fig. 26, arrows). Internally, raphe straight, continuing from pole to pole where its distal raphe fissure curves into raised helictoglossa (Figs 26, 27). Type:��� CHINA. Hunan province: West Dongting Lake, Yang���s Village, a sampling point near the lakeshore, 28�� 52��� 29.5��� N, 112�� 16��� 52��� E, 50 m asl., Bing Liu, 23 rd April 2017 (holotype BM! 81944, specimen circled on slide, illustrated as Fig. 1; isotype JIU! G202101, specimen circled on slide, illustrated as Fig. 3). Etymology:���Named after China where the species was found (the specific locality is Dongting Lake). Ecology:��� Bacillaria sinensis was commonly found in the surface sediment collected in West Dongting Lake. Associated species comprised Entomoneis triundulata Bing Liu & D.M. Williams (in Liu et al. 2018: 242), Ulnaria dongtingensis Bing Liu (in Liu et al. 2019: 127), and some species of Navicula Bory (1822: 128), Nitzschia Hassall (1845: 435), Sellaphora Mereschkowsky (1902:186), Surirella Turpin (1828: 362, 363), Tryblionella Smith (1853: 35), and others. The following environmental parameters were measured in the field. Conductivity was 109.3 �� 0.1 ��S��� cm-1, pH was 8.3 �� 0.2 and water temperature was 23.5 �� 0.3 ��C. Since the diatom sample was collected using lens tissue from the mud surface and the water conductivity is above 100 ��S��� cm-1, Bacillaria sinensis can be considered an epipelic alkaliphilous diatom characteristic of moderate electrolyte content in freshwaters., Published as part of Long, Ji-Yan, Williams, David M., Liu, Bing & Zhou, Yang-Yan, 2021, Two new freshwater species of Bacillaria (Bacillariophyta) from Dongting Lake, China, pp. 243-256 in Phytotaxa 513 (3) on pages 245-249, DOI: 10.11646/phytotaxa.513.3.4, http://zenodo.org/record/5310508, {"references":["Liu, B., Williams, D. M. & Ector, L. (2018) Entomoneis triundulata sp. nov. (Bacillariophyta), a new freshwater diatom species from Dongting Lake, China. Cryptogamie, Algologie 39: 239 - 253. https: // doi. org / 10.7872 / crya / v 39. iss 2.2018.239","Liu, B., Williams D. M., Blanco S., Liu Z. - X. & Liu, D. (2019) Three new species of Ulnaria (Kutzing) Compere (Bacillariophyta) from China, with reference to the fine structure of their valvocopula. Cryptogamie, Algologie 40: 119 - 139. https: // doi. org / 10.5252 / cryptogamie-algologie 2019 v 40 a 11.","Bory de Saint-Vincent, J. B. G. M. (1822) Bacillarees. Dictionaire Classique d'Histoire Naturelle 2: 127 - 129.","Hassall, A. H. (1845) A history of the British freshwater algae, including descriptions of the Desmideae and Diatomaceae, with upwards of one hundred plates, illustrating the various species. I. Highley, London, 462 pp. https: // doi. org / 10.5962 / bhl. title. 22609","Mereschkowsky, C. (1902) On Sellaphora, a new genus of diatoms. Annals and Magazine of Natural History, Series 7 9: 185 - 195. http: // doi. org / 10.1080 / 00222930208678565","Turpin, P. J. F. (1828) Observations sur le nouveau genre Surirella. Memoires du Museum d'Histoire Naturelle 16: 361 - 368.","Smith, W. (1853) Synopsis of British Diatomaceae. John Van Voorst, London, 89 pp."]}

Bacillaria dongtingensis Bing Liu & D.M. Williams sp. nov. (Figs 30–58) LM: Valves linear-lanceolate, tapering to cuneate or rostrate (Figs 30–40). Valve dimensions (n = 81): 53–99 μm long, 4.4–5.7 μm wide. Fibulae distinct, placed approximately along valve midline, unevenly spaced, 6–12 in 10 μm. Striae indistinct, parallel throughout valve, 24–26 in 10 μm. Fault sites on valve broader side difficult to discern using LM. SEM: Colony and frustule view: Cell to cell attachment forms colony (Fig. 41). At least two open girdle bands (Figs 43–46, labeled B1 to B2). Poroids of valvocopula covered externally by hymenes (Figs 45, 46). TABLE 1. Comparison among similar Bacillaria species. Valve view: Valve linear-lanceolate (Figs 41, 43, 47, 53). Raphe nearly central, continuous from pole to pole, distal raphe endings T-shaped (Figs 45, 46, 49, 52); one raphe flange present on narrower side of valve, irregular or complete lacking, terminating before reaching poles (Figs 42–52, RF). Transapical ribs originated with raphe ribs, parallel; striae uniseriate, composed of rounded areolae covered by hymenes externally, continuing onto mantle. Marginal spines distinct (e.g., Figs 44–46, 48, 49). On broader side of valve, transapical rib forms two branches at some sites (Figs 42, 50, 51, 52, 55, 57, arrow, respectively; 58, two arrows), sometimes two transapical ribs merge into one (Figs 42, 48, 50, 54, 55, three curved arrows, respectively). Fibulae rib-like, arching into cell (Figs 53–58). Two fibular ribs asymmetrical, i.e. fibular rib on broader side of valve more developed than that on narrower side (Figs 54, 56, FR). Internally, raphe straight, continuing from pole to pole where its distal raphe fissure curves into raised helictoglossa (Figs 55, 56). Type:— CHINA. Hunan province: West Dongting Lake, Yang’s Village, a sampling point near the lakeshore, 28°52’29.5” N, 112°16’52” E, 50 m asl., Bing Liu, 23 rd April 2017 (holotype BM! 81955, specimen circled on slide, illustrated as = Fig. 30; isotype JIU! G202102, specimen circled on slide, illustrated as Fig. 32). Etymology:—Named after Dongting Lake, where the species was found. Ecology:— Bacillaria dongtingensis was commonly found in the surface sediment collected in West Dongting Lake with B. sinensis. For details see above.

Bacillaria dongtingensis Bing Liu & D.M. Williams sp. nov. (Figs 30���58) LM: Valves linear-lanceolate, tapering to cuneate or rostrate (Figs 30���40). Valve dimensions (n = 81): 53���99 ��m long, 4.4���5.7 ��m wide. Fibulae distinct, placed approximately along valve midline, unevenly spaced, 6���12 in 10 ��m. Striae indistinct, parallel throughout valve, 24���26 in 10 ��m. Fault sites on valve broader side difficult to discern using LM. SEM: Colony and frustule view: Cell to cell attachment forms colony (Fig. 41). At least two open girdle bands (Figs 43���46, labeled B1 to B2). Poroids of valvocopula covered externally by hymenes (Figs 45, 46). TABLE 1. Comparison among similar Bacillaria species. Valve view: Valve linear-lanceolate (Figs 41, 43, 47, 53). Raphe nearly central, continuous from pole to pole, distal raphe endings T-shaped (Figs 45, 46, 49, 52); one raphe flange present on narrower side of valve, irregular or complete lacking, terminating before reaching poles (Figs 42���52, RF). Transapical ribs originated with raphe ribs, parallel; striae uniseriate, composed of rounded areolae covered by hymenes externally, continuing onto mantle. Marginal spines distinct (e.g., Figs 44���46, 48, 49). On broader side of valve, transapical rib forms two branches at some sites (Figs 42, 50, 51, 52, 55, 57, arrow, respectively; 58, two arrows), sometimes two transapical ribs merge into one (Figs 42, 48, 50, 54, 55, three curved arrows, respectively). Fibulae rib-like, arching into cell (Figs 53���58). Two fibular ribs asymmetrical, i.e. fibular rib on broader side of valve more developed than that on narrower side (Figs 54, 56, FR). Internally, raphe straight, continuing from pole to pole where its distal raphe fissure curves into raised helictoglossa (Figs 55, 56). Type:��� CHINA. Hunan province: West Dongting Lake, Yang���s Village, a sampling point near the lakeshore, 28��52���29.5��� N, 112��16���52��� E, 50 m asl., Bing Liu, 23 rd April 2017 (holotype BM! 81955, specimen circled on slide, illustrated as = Fig. 30; isotype JIU! G202102, specimen circled on slide, illustrated as Fig. 32). Etymology:���Named after Dongting Lake, where the species was found. Ecology:��� Bacillaria dongtingensis was commonly found in the surface sediment collected in West Dongting Lake with B. sinensis. For details see above., Published as part of Long, Ji-Yan, Williams, David M., Liu, Bing & Zhou, Yang-Yan, 2021, Two new freshwater species of Bacillaria (Bacillariophyta) from Dongting Lake, China, pp. 243-256 in Phytotaxa 513 (3) on pages 249-254, DOI: 10.11646/phytotaxa.513.3.4, http://zenodo.org/record/5310508, {"references":["Jahn, R. & Schmid, A. - M. M. (2007) Revision of the brackish-freshwater diatom genus Bacillaria Gmelin (Bacillariophyta) with the description of a new variety and two new species. European Journal of Phycology 42: 295 - 312. https: // doi. org / 10.1080 / 09670260701428864","Spaulding, S. (2018) Bacillaria paxillifera. In Diatoms of North America. Retrieved April 20, 2021 from [https: // diatoms. org / species / bacillaria _ paxillifera]"]}

Pinnularia qinghainensis Bing Liu & S. Blanco sp. nov. (Figs 1–25) LM: Valves linear with broadly rounded apices (Figs 1–15), dimensions (n=31): 35–70 μm long, 8–11μm wide. Sternum narrow, widening towards central area. Central area hexagonal with three forms: reaching both margins (e.g. Figs 1, 5, 11), meeting one margin and bordering the other with few short striae (e.g. Figs 2, 3), or bordering both margins with a few short striae (e.g. Figs 8, 12, 15). Raphe filiform, straight. Proximal raphe ends slightly bent toward same side with drop-shaped central pores. Distal raphe fissures sickle-shaped, deflexed to same side. Striae mostly curved, radiate at middle, gradually becoming convergent when approaching apices. Striae 13–16 (often 14) in 10 μm at centre, 15–17 in 10 μm near apices. Longitudinal lines absent. SEM: Valves linear with broadly rounded apices (Figs 16, 21). Central area hexagonal, reaching both margins (Figs 17, 23), or bordering both margins with a few short striae (Figs 21, 22). External proximal raphe ends bent in one direction, slightly dilated (Fig. 17). Distal raphe fissures hooked towards same side (Figs 16, 18, 19). Internally, raphe branches straight, proximal raphe fissures curved towards same side, central nodule not raised (Figs 22, 23); distal raphe terminating as helictoglossae (Figs 24, 25). Striae mostly composed of 4 rows of small areolae (rarely 3 rows) (Figs 16–20), covered by silicified plates (Fig. 20); internally, alveoli open, their openings as depressed chambers. Type:— CHINA. Qinghai province: Lake Qinghai, a sampling point near the lakeshore (see Liu et al. 2020, fig. 1, sampling site 1), 36°50’34” N, 99°42’39” E, 3210 m asl, Bing Liu, 19 th July 2019 (holotype BM! 98361= Fig. 2; isotype JIU! G202002 = Fig. 3). Etymology: —Named after Lake Qinghai, where the species was found. Ecology: —The following environmental parameters were measured in the field: Electrical conductance 16296.7 ± 86.2 µS∙ cm-1; pH 9.14 ± 0.01; water temperature 15.5 ± 0.3 °C. Similar taxa: Pinnularia boliviana S. Blanco, Álvarez-Blanco & Cejudo-Figueiras (in Blanco et al. 2013: 15), P. rhombarea var. halophila Krammer ( 2000: 76) and P. halophila Krammer (1992: 146; see also Krammer 2000: 137) all live in brackish water and in some respects are similar to P. qinghainensis. Pinnularia boliviana differs from P. qinghainensis by its lower stria density (12–13 vs. 13–16 in 10 μm), its wider valves (10.8–16.4 vs. 8–11 μm), and its fascia (in P. qinghainensis the central area may not constitute a fascia). Pinnularia rhombarea var. halophila has broader valves (12–15 vs. 8–11μm) and lower stria density (10–11 vs. 13–16 in 10 μm). Pinnularia halophila has broader valves (17–22 vs. 8–11μm) and much lower stria density (8–9 vs. 13–16 in 10 μm). Pinnularia brebissonii (Kützing 1844: 93) Rabenhorst (1864: 222) also has a lower stria density than P. qinghainensis (12–13 vs. 13–16 in 10 μm). Pinnularia qinghainensis is only known from the type locality and is a rare species (its relative abundance is ca. 0.4%). The diatom samples that included P. qinghainensis were scraped off from stone surfaces immersed in brackish water, hence, the species may be recognized as a brackish-water epilithic diatom. Most of the companion species (e.g. Ctenophora sinensis Bing Liu & D.M. Williams (in Liu et al. 2020: 119), Entomoneis spp., Halamphora spp., Berkeleya sp., Triblionella spp., Brachysira sp. and Surirella spp.) in the samples are either marine or brackish-water diatoms which will be reported later.

Pinnularia qinghainensis Bing Liu & S. Blanco sp. nov. (Figs 1–25) LM: Valves linear with broadly rounded apices (Figs 1–15), dimensions (n=31): 35–70 μm long, 8–11μm wide. Sternum narrow, widening towards central area. Central area hexagonal with three forms: reaching both margins (e.g. Figs 1, 5, 11), meeting one margin and bordering the other with few short striae (e.g. Figs 2, 3), or bordering both margins with a few short striae (e.g. Figs 8, 12, 15). Raphe filiform, straight. Proximal raphe ends slightly bent toward same side with drop-shaped central pores. Distal raphe fissures sickle-shaped, deflexed to same side. Striae mostly curved, radiate at middle, gradually becoming convergent when approaching apices. Striae 13–16 (often 14) in 10 μm at centre, 15–17 in 10 μm near apices. Longitudinal lines absent. SEM: Valves linear with broadly rounded apices (Figs 16, 21). Central area hexagonal, reaching both margins (Figs 17, 23), or bordering both margins with a few short striae (Figs 21, 22). External proximal raphe ends bent in one direction, slightly dilated (Fig. 17). Distal raphe fissures hooked towards same side (Figs 16, 18, 19). Internally, raphe branches straight, proximal raphe fissures curved towards same side, central nodule not raised (Figs 22, 23); distal raphe terminating as helictoglossae (Figs 24, 25). Striae mostly composed of 4 rows of small areolae (rarely 3 rows) (Figs 16–20), covered by silicified plates (Fig. 20); internally, alveoli open, their openings as depressed chambers. Type:— CHINA. Qinghai province: Lake Qinghai, a sampling point near the lakeshore (see Liu et al. 2020, fig. 1, sampling site 1), 36°50’34” N, 99°42’39” E, 3210 m asl, Bing Liu, 19 th July 2019 (holotype BM! 98361= Fig. 2; isotype JIU! G202002 = Fig. 3). Etymology: —Named after Lake Qinghai, where the species was found. Ecology: —The following environmental parameters were measured in the field: Electrical conductance 16296.7 ± 86.2 µS∙ cm-1; pH 9.14 ± 0.01; water temperature 15.5 ± 0.3 °C. Similar taxa: Pinnularia boliviana S. Blanco, Álvarez-Blanco & Cejudo-Figueiras (in Blanco et al. 2013: 15), P. rhombarea var. halophila Krammer ( 2000: 76) and P. halophila Krammer (1992: 146; see also Krammer 2000: 137) all live in brackish water and in some respects are similar to P. qinghainensis. Pinnularia boliviana differs from P. qinghainensis by its lower stria density (12–13 vs. 13–16 in 10 μm), its wider valves (10.8–16.4 vs. 8–11 μm), and its fascia (in P. qinghainensis the central area may not constitute a fascia). Pinnularia rhombarea var. halophila has broader valves (12–15 vs. 8–11μm) and lower stria density (10–11 vs. 13–16 in 10 μm). Pinnularia halophila has broader valves (17–22 vs. 8–11μm) and much lower stria density (8–9 vs. 13–16 in 10 μm). Pinnularia brebissonii (Kützing 1844: 93) Rabenhorst (1864: 222) also has a lower stria density than P. qinghainensis (12–13 vs. 13–16 in 10 μm). Pinnularia qinghainensis is only known from the type locality and is a rare species (its relative abundance is ca. 0.4%). The diatom samples that included P. qinghainensis were scraped off from stone surfaces immersed in brackish water, hence, the species may be recognized as a brackish-water epilithic diatom. Most of the companion species (e.g. Ctenophora sinensis Bing Liu & D.M. Williams (in Liu et al. 2020: 119), Entomoneis spp., Halamphora spp., Berkeleya sp., Triblionella spp., Brachysira sp. and Surirella spp.) in the samples are either marine or brackish-water diatoms which will be reported later., Published as part of Deng, Li-Ying, Blanco, Saúl, Liu, Bing, Quan, Si-Jin & Long, Ji-Yan, 2021, Pinnularia qinghainensis: a new diatom species (Bacillariophyta) found in the brackish Lake Qinghai, China, pp. 80-84 in Phytotaxa 483 (1) on pages 80-81, DOI: 10.11646/phytotaxa.483.1.5, http://zenodo.org/record/5420266, {"references":["Liu, B., Williams, D. M., Liu, Z. X. & Chen, J. H. (2020) Ctenophora sinensis: a new diatom species (Bacillariophyta) from China with comments on its structure, nomenclature and relationships. Phytotaxa 460 (2): 115 - 128. https: // doi. org / 10.11646 / phytotaxa. 460.2.1","Blanco, S., Irene, A. B., Cristina, C. F., Ignacio, D. G., Eloy, B., Raul, M., Hector, O. G., Virginia, A. V. & Roberto, S. (2013) New diatom taxa from high-altitude Andean saline lakes. Diatom Research 28 (1): 13 - 27. https: // doi. org / 10.1080 / 0269249 X. 2012.734528","Krammer, K. (2000) The genus Pinnularia. In: Lange-Bertalot, H. (Ed.) Diatoms of Europe. Diatoms of the European Inland waters and comparable habitats. Vol. 1. A. R. G. Gantner Verlag, K. G., Ruggell, 703 pp.","Krammer, K. (1992) Pinnularia, eine Monographie der europaischen Taxa. Bibliotheca Diatomologica 26: 1 - 353.","Kutzing, F. T. (1844) Die Kieselschaligen Bacillarien oder Diatomeen. W. Kohne, Nordhausen, 152 pp. https: // doi. org / 10.5962 / bhl. title. 64360","Rabenhorst, L. (1864) Flora europaea algarum aquae dulcis et submarinae. Sectio I. Algas diatomaceas complectens, cum figuris generum omnium xylographice impressis. Lipsiae [Leipzig]: Apud Eduardum Kummerum, 359 pp. https: // doi. org / 10.5962 / bhl. title. 7029"]}

Deng, Li-Ying, Blanco, Saúl, Liu, Bing, Quan, Si-Jin, Long, Ji-Yan (2021): Pinnularia qinghainensis: a new diatom species (Bacillariophyta) found in the brackish Lake Qinghai, China. Phytotaxa 483 (1): 80-84, DOI: 10.11646/phytotaxa.483.1.5, URL: http://dx.doi.org/10.11646/phytotaxa.483.1.5