Two new species of the genus Lacustriella (Bacillariophyta) from Lake Baikal Author Rodionova, Yelena V. Author Pomazkina, Galina V. Author Sherbakova, Tatyana A. tsherb@lin.irk.ru text Phytotaxa 2024 2024-06-12 652 4 261 272 http://dx.doi.org/10.11646/phytotaxa.652.4.2 journal article 10.11646/phytotaxa.652.4.2 1179-3163 13216815 Lacustriella acutocuneata Metzeltin, Lange-Bertalot & Kulikovskiy 2012 Light microscopy (LM): ( Figs 47–56 ). Valves linear-elliptic-lanceolate with slightly concave margins and rostrate apices. Valve length 48.5–67.0 μm, width 18–19 μm. External axial area narrow at apices, gradually expanding into the weakly defined central area. Raphe filiform, central endings straight, terminal ends bent to opposite sides. Striae uniseriate, slightly radial proximally, become radial towards apices, 11–12 in 10 μm. One longitudinal canal along each margin. Scanning electron microscopy (SEM): ( Figs 57–64 ). Externally, areolae in striae small, round, open, in depressions, 12–15 in 10 μm, slightly irregular in the central part of the valve. Proximal areolae near axial and central areas enlarged, rounded ( Fig. 58 ). Distal areolae along the longitudinal canals appear binary due to narrowed vimines ( Figs 58, 59 ), with the outer ones somewhat larger and elongate. The surface of longitudinal canals is smooth, unornamented ( Fig. 58 ). Proximal raphe endings lay in slightly elongated drop-shaped depressions ( Fig. 59 ). Distal endings smoothly curved to opposite sides and onto the mantle ( Figs 61, 62 ). Internally, areolae in striae covered with hymenes. Raphe endings terminate on helictoglossae, central helictoglossae merged ( Figs 63, 64 ). The species was commonly observed in many sites of all three basins of Lake Baikal, including Anga Bay, the vicinity of Cape Khoboi on Olkhon island, near Сape Tonkiy and the area of Cape Kabaniy.