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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

Psammothidium lacustre Enache & Potapova sp. nov. (Figs 1–8, 35–39) Valvae lanceolate, 8.4–11.2 µm latae, 16.7–28 µm longae. Raphovalva cum area axialis linearis versus centro expanso, area centralis rectangularis, ½ 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 µm; areolae cum foramina externae circulares, foramina internae transapicalem elongatae, 40–60 in 10 µm. Valves lanceolate, 8.4–11.2 µm wide, 16.7–28 µm long. Raphe valve with linear axial area, rectangular central area, occupying ½ 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 µm; areolae 40–60 in 10 µm, 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 µm, 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 (