The shell is dull cinnamon brown, similar to Agathotoma neglecta but differs by the spiral sculpture, which in A. neglecta is of very even and uniform threads, while in our species the threads are unequal, every third or fourth one a little larger; towards the anterior end they become decidedly coarser. The nucleus is somewhat worn, but appears to consist of 2 ½ whorls, the first smooth, the rest finely ribbed axially. The first post-nuclear whorl has about ten rather strong ribs, with a spiral cord midway between sutures, another in the lower suture. The ribs then become larger, more widely spaced, rather sharp-edged, continuous from whorl to whorl on the last three whorls, six (including the varix) on the last whorl, where they become obsolete near the anterior end. The narrow aperture is but little contracted anteriorly. The anal sinus is rather large, with a heavy callus on the left side; lips smooth within. Columella straight.
Length 6 mm., diam. 2.3 mm.; about 7 1/2 whorls.

Ithycythara penelope is a shorter shell, more contracted at the sutures.

West Coast of Central America. Type location: San Juan del Sur, Nicaragua.