Guide to Oricymba

SPECIES OF ORICYMBA ARE NOT KNOWN TO OCCUR IN NORTH AMERICA

This genus has slightly dorsiventral, or nearly symmetric, valves. The valve face is flat and is separated from the valve mantle by a marginal ridge. A distinct, isolated stigma is present, located between the central nodule and the ventral striae. The raphe is slightly lateral. Proximal raphe ends are widened slightly and deflected to the primary side. Distal raphe fissures are dorsally deflected. The striae are uniseriate, but may be (rarely) biseriate, and extend onto the valve mantle. Externally, the expression of the areolae are as elongated slits, partially occluded by dentate projections. Two apical pore fields are present.

A number of species are included within Oricymba; all are known from the Indian subcontinent, southeast Asia, China, Korea and Japan in areas of low nutrient and low alkalinity waters.