Gyroidinopsis McCulloch 1977

Test robust, trochospiral, spiral side slightly convex, all of the three rapidly enlarging whorls visible although early ones are partially obscured by clear calcite in the umbonal region, chambers increasing very little in height as added, about twelve in the final whorl, sutures straight, radial, thickened, and flush with the surface, on the umbilical side a ridge about midway between the periphery and the umbilicus marks the sharply angled umbilical shoulder that borders the deeply excavated umbilical margin, sutures flush at the outer end of the chambers but incised inward from the shoulder ridge to a small umbilical plug, periphery broadly rounded; wall calcareous, hyaline, translucent, finely perforate except the umbilical ends of the chambers that are imperforate from the umbilical shoulder inward; aperture interiomarginal, a low equatorial arch bordered by a narrow lip but not extending onto either spiral or umbilical side. Holocene; off Mexico, USA: California. (Loeblich & Tappan, 1987, Foraminiferal Genera and Their Classification)