rotaliidæ

Century Dictionary and Cyclopedia

1. A family of rhizopods whose test is calcareous, perforate, free or adherent, typically spiral, and rotaliform—that is to say, coiled in such a manner that the whole of the segments are visible on the superior surface, those of the last convolution only on the inferior or apertural side, sometimes one face being more convex, sometimes the other. Aberrant forms are evolute, outspread, acervuline, or irregular. Some of the higher modifications have double chamberwalls, supplemental skeleton, and a system of canals. See cut under Rotalia.