Sigmopyrgo Hofker 1983

Test large, up to 1.5 mm in diameter, subglobular, megalospheric test biloculine throughout, microspheric test with numerous chambers one-half coil in length, arranged in varying planes in the early stage to result in a sigmoid series for up to as many as eighteen or nineteen chambers, later chambers planispiral and alternately added on opposite sides as in Pyrgo, chambers without floors but added against the previous test surface; wall thick, calcareous, porcelaneous, peripheral margin crenulate; aperture at the end of the final chamber, a broad low sinuate arch, with a similarly broad low flaplike tooth that may be slightly indented in the median plane to appear almost bifid, aperture bordered by an irregularly thickened rim. Holocene; Atlantic; Caribbean; central Pacific. (Loeblich & Tappan, 1987, Foraminiferal Genera and Their Classification)