Stauroneis sacajaweae Bahls, sp. nov. (Figs 9–15)

Type: — USA. Montana: Spring at base of Square Butte, tributary of Cowboy Creek, Chouteau County, 47.4829 o N, 110.2380 o W, 1400 m elevation, collected from rocks and sediment by Loren Bahls, 22 May 1999. MDC sample 179801 ; holotype slide MDC B1-22-5, Figs 9, 11–15.

Valves lanceolate with gradually attenuated subrostrate apices. A deep pseudoseptum occupies each apex (Fig. 15). Valve length 54–80 µm; valve width 10.8–14.7 µm. Raphe lateral, becoming filiform towards proximal ends, which are bent to one side and tipped with weakly inflated pores. Distal raphe ends hooked in a direction opposite that of proximal ends. Axial area c 3 x wider than raphe and widens gradually towards central area. Central stauros broad, shaped like a bow tie. Striae strongly radiate throughout, 23–25 in 10 µm. Areolae in striae 18–22 in 10 µm.

Etymology:—This species is named after the Lemhi Shoshone woman, Sacajawea (1788–1812?), who served as guide and interpreter for Lewis and Clark (Mann 2004).

Observations: — Stauroneis sacajaweae was reported by Bahls (2010: 155) as S. subhyperborea Van de Vijver & Lange-Bertalot (2004: 72) . However, the Montana specimens have a wider stauros and distinctly higher stria and areola densities than S. subhyperborea . Besides the type locality—which it shares with S. clarkii — S. sacajaweae has been collected from a seep along the Going-To-The-Sun Road in Glacier National Park, Montana, 48.7381 o N, 113.7456 o W.