As Anachis carmen (synonym)
The oblong-conic shell is chaetura-drab with chamois or cream-buff ribs. The spire has slightly convex lateral outlines and acute apex. Ten whorls, the first three buff and smooth; the rest with axial sculpture of rounded ribs which are smooth and continuous from whorl to whorl; these ribs are absent on the anterior extension of the last whorl, and are more or less shortened on the back. Spiral sculpture of impressed linear spirals in the intercostal intervals, becoming continuous, deeper, with strongly convex interspaces on the anterior part of the last whorl. There are about six well marked spiral impressions on the penult whorl. The aperture is brown within the lips, bluish inside. Outer lip is somewhat thickened outside, with a small sinus near the posterior end, a series of about five teeth below the sinus. Inner lip is weakly rugose near the base.
Length 9 mm., diam. 3.5 mm.

Biconic, axially ridged species 7 to 9 mm long and less than half as wide, uniformly dark brown with yellowish lines atop the axial ridges, and spiral grooves between ridges.
Shell medium-sized, biconic, 7.60 to 8.57 (avg. 8.08) mm long and 2.95 to 3.58 (avg. 3.20) mm wide in eight specimens measured. Adults have 6.25 to 7 (avg. 6.6) teleoconch whorls. Protoconch smooth, tan, with 3 whorls (in four specimens) and a moderate velar sinus. Shell dark grey or brown, nearly black, with light yellowish axial stripes on the tops of the axial ridges that are the predominant sculpture. Shell has close-set spiral grooves between axial ridges, and a weak subsutural groove. Axial ridges fade on dorsal side of body whorl. Aperture narrow and darkly pigmented, with a posterior notch in the aperture edge, labial denticles and a parietal ridge. Body coloration: Preserved animals densely mottled with black blotches overall, sole of foot cream colored. Cephalic tentacles white with medial black bands. Siphon densely spotted with black.
Operculum: Operculum elongate oval, more pigmented in the middle. There is a keel and a bilobed muscle scar.
Radula: Radula narrow, with lateral teeth 35 to 40 µm long in two specimens dissected. Center plates are about twice as wide as deep. Each lateral tooth has three secondary cusps, with basal cusp similar to the other two, and embedded in membranes. The radula in one specimen had 125 tooth rows.

This species has been placed in Parvanachis in recent years perhaps because of its small size; it does not have a globose shell form, and the radula, though similar to those of the Parvanachis species, lacks the down-hooked shape of the basal cusp of the lateral teeth. It also doesn't closely resemble any other Panamic species. More important though, the reproductive anatomy is considerably different than that of any species of Parvanachis. Species with similar anatomy occur in both Costoanachis and Anachis, but these two genera as currently known are both anatomically and morphologically diverse. Costoanachis was unfortunately based on a Neogene fossil species (Columbella (Anachis) turrita Sacco, 1890, renamed by Radwin (1977b) Costoanachis saccostata) from Europe, so cannot be anatomically characterized. Anachis is based on the large Panamic species Anachis scalarina, but the genus name is widely used for axially ribbed species. The reproductive anatomy of A. scalarina is similar to that of this species and other Anachis and Costoanachis species described by Marcus & Marcus (1962) and Houston (1976). Radwin (1977b) interprets Costoanachis as confined to species that lack axial ridges on some portion of the shell spire. Insomuch as this species has axial ridges over the entire spire, it is anatomically similar to Anachis scalarina, and considering it probably is not possible to determine exactly what Costoanachis actually is due to lack of anatomical and molecular data, this species should be referred to as Anachis pardalina until a global systematic analysis can be carried out.