Shell minute, elongate-conic, pale yellowish with a narrow brown spiral band a little below the middle of the whorls; nuclear whorls 2,5 , relatively large, planorbid, with the axis at right angles to that of the following whorls, in the first of which they are slightly immersed; postnuclear whorls 8, well rounded, sutures impressed; axial sculpture of nearly vertical, slightly sinuous ribs, of which 16 appear on the early whorls, gradually increasing to 24 on the last whorl; interspaces about as wide as the ribs, marked with 2 spiral series of broad pits near the base, above which are about 12, equally spaced, incised, spiral lines; periphery of last whorl well rounded, marked by a narrow, smooth band; base rather long, well rounded, marked by a single spiral series of pits just below the periphery, then a second, narrow, smooth band, followed by 5 fine, incised, spiral lines; aperture oval, outer lip thin, showing the external sculpture within; columella slender, curved. The type measures: length, 2.8 mm; diameter, 0.7 mm.
Holotype: No. 752 (Calif. Acad. Sci. Paleo. Type Coll.), from Loc. 27,229 (C.A.S.), dredged in from 3 to 9 fms. in Bahia Honda, Panama. L. G. Hertlein collector. Eight additional specimens were dredged at the same locality.
In the key given by Dall & Bartsch to the west coast species in the subgenus Pyrgiscus this would follow almo, and amandi of this paper from which it differs in the much smaller size and different arrangement of the spiral series of pits.
This species is named for the late Dr. Barton Warren Evermann, formerly Director of the California Academy of Sciences and of the Steinhart Aquarium.