Shell elongate-conic, white; nuclear whorls 3, smooth, well rounded; postnuclear whorls 6, rounded, with the point of greatest diameter a little above the impressed suture; axial sculpture of low, strongly protractive ribs which fade out at the suture, of these 18 appear on the first whorl, increasing to about •10 on the penultimate whorl; spiral sculpture of slender threads in the interspaces between the ribs, 10 appearing on the first whorl, increasing to 16 on the penultimate whorl; on the first whorl a median spiral thread is much the strongest, angulating the whorl, and a second, just above the suture, is only a little less strong, on the second whorl the median thread fades out while the one above the suture remains the strongest throughout the remaining whorls, the remainder of the threads being subequal and subequally spaced; periphery,rounded, base somewhat produced, with 15 spiral cords distinctly stronger than the spiral threads on the spire, with, in the interspaces on the upper part of the base, feeble extensions of the axial ribs; aperture ovate, slightly channeled posteriorly and anteriorly, outer lip with a thick callus immediately behind the edge, body with a strong callus. The type measures: length, 4.8 mm.; diameter 1.8 mm.
Holotype near Port Parker, Costa Rica, dredged in 12 fath¬oms (22 meters), shelly mud. Specimens also were dredged at Station 200-D-19, Lat. 12° 28' 03" N., Long. 87° 12' 39" W., near Corinto, Nicaragua, in 12-13 fathoms (22-24 meters), mangrove leaves.
This species bears a resemblance to Rissoina townsendi Bartsch but differs in that the axial ribs are much more protractive.