(Wallich)
Diagnosis: Ovate main chamber, with hollow spine at aboral pole, separated by an internal diaphragm and partially by an external constriction from secondary chamber, nearly as large as main chamber. Secondary chamber connected to main chamber by eccentric tube through diaphragm. Secondary chamber broadly curved to open at about right angle to main axis, lower lip of peristome may be extended as spine, or connect through a broadly arched filamentous bar (probably normal, but seldom preserved) to aboral spine. Surface with longitudinal striae.
Length: 0.037-0.048 mm.