Halamphora elongata Bennett & Kociolek, 2014

You, Qingmin, Kociolek, John Patrick & Wang, Quanxi, 2015, Taxonomic studies of the diatom genus Halamphora (Bacillariophyceae) from the mountainous regions of southwest China, including the description of two new species, Phytotaxa 205 (2), pp. 75-89 : 81-82

Halamphora elongata Bennett & Kociolek ( Figs. 35–54 )

Description:— Valves with strongly convex dorsal margin. Ventral margin concave and more or less tumid in the valve center. Valve ends small, rostrate to capitate. Length 28.6–56.0 μm, valve breadth 9.6–11.6 μm. Externally, the raphe is contained within a rib, particularly well developed along the dorsal portion of the axial area ( Fig. 51 ). Both proximal and distal external raphe ends are deflected or curved towards the dorsal margin of the valve ( Figs. 51, 53 ). External proximal raphe ends narrowly rounded ( Fig. 51 ). Axial area linear. Central area asymmetric to rounded formed by shortened central ventral striae and dorsal striae ( Fig. 51 ). Dorsal striae radiate with dash-like areolae ( Figs. 49, 51 ), 18–21/ 10 μm at mid-valve, 22–23/ 10 μm μm near the ends. Ventral striae composed of short dashes 22–26/ 10 μm. Internally, the striae possess dash-like areolea ( Figs. 50, 52 ), the thickened virgae of the central striae are evident near the dorsal side ( Figs. 50, 52 ). The proximal raphe ends terminate at a narrow central helictoglossae ( Fig. 52 ). Distally, the internal raphe ends terminate as helictoglossae ( Fig. 54 ).

Distribution and ecology:— Namtso Lake, Tibet, China, altitude 4729 m a.s.l., pH 9.7, water temperature 16 ºC, collected in the pond near the Namtso Lake, with many Chara sp. in the water.

Observations:— Our species has similar striae structure with Amphora veneta var. subcapitata Kisselev (1932: 87) , but has a different valve outline. Halamphora elongata is similar to A. mira Krasske (1949: 85) , however the obvious difference is that the latter species is larger (Length 40–80 μm, valve breadth 9–14 μm.) and lacks the thickened central virgae seen in Tibet specimens.

Figures

FIGURES 35–48. Halamphora elongata, LM. Valve views showing size diminution series. Scale bars = 10 μm for all figures.

FIGURES 49–54. H. elongata. SEM. 49, 51, 53. External views. 49. Entire valve showing shape of the valve. 51. View of central area with proximal raphe ends curved towards the dorsal margin. 53.View of valve end with curved raphe end. 50, 52, 54. Internal views. 50. Entire valve view. 52. Central area with evident thickened virgae. 54. View of valve end, with prominent helictoglossa. Scale bars shown in each figure.