Plagiopyxis intermedia var.  cyrtostoma  Bonnet, 1961

Diagnosis: Shell clear, fairly transparent, circular or very slightly elliptical in dorsal view. Semi-elliptical in side view; as in the type, the ventral side bends moderately; the dorsal lip draws an arc of a circle of approximately 90° and 15 µm in radius. The pseudostome, in narrow fissure, is bordered by a very thin chitinoid bead. The covering comprises, on the dorsal face, large reworked amorphous siliceous plates, connected by very small elements, also siliceous, embedded in a finely punctuated light yellow cement. The dorsal black elements, characteristic of the type, are only rarely present. On the ventral side, the siliceous plates are generally smaller.

Dimensions: Length 70-80 µm; width 70-80 µm; dorso-ventral (height) 35-45 µm.

Ecology: This species is frequent in all the alkaline skeletal soils of the Pyrenean region (particularly in the vicinity of the Col de Soulor, Hautes-Pyrénées).