Shell small (length, 8.6 mm., height, 4.15 mm.), short, conic, the length nearly twice the height, fairly solid, the bluntly truncated apex perforated by an oblong or slightly trilobate orifice placed in the anterior one-third. The longer posterior slope is noticeably arched or convex, the shorter anterior slope nearly straight and steep. Basal margin is oblong-ovate, not quite flat, the middle 2one being weakly concave, the anterior end slightly narrowed, the sides nearly straight, the marginal edge coarsely serrated by the projecting ends of the ribs in an alternating manner, the ends of the ribs internally fluted. The sculpture is cancellated or latticed by intersecting coarse, radial riblets and coarse, concentric threads arranged symmetrically, with nine primary ribs on each side (total 18), the details of which are as follows: the primary ribs are coarse, high, narrow, and rather widely spaced, with a similar but much smaller secondary riblet in the middle of each interspace and in addition with two or three much smaller tertiary radial threads lying in each section of the divided main interspace; the concentric threads are developed in two strengths, a large, coarse, primary set of narrow, flangelike ridges which bridge across the primary interspaces (about 10 in number), packed close together on the apical section, wider and more regularly spaced towards the base, and a set of much finer, concentric threads cutting across radial ribs forming small nodes. At the intersection of the primary ribs and the concentrics, the resulting nodes are high and sharp. External color is a cream or light, greenish gray, mottled irregularly with black, the secondary riblets are often black. Internally, the callus around the orifice is quite large, sharply truncated on the posterior end, white or gray, the transmitted images of the primary ribs and concentrics showing as narrow, white bars and their intervals as interrupted black lines.
Holotype, length, 8.6 mm.; height, 4.5 mm.; width, 5.5 mm. ANSP 211878. Bocas Island.
This species differs from juvenile specimens of D. listeri (d'Orbigny) by its higher, more conic form, smaller, oblong orifice and finer sculpture, there being a greater difference in size between the primary and secondary riblets. D. alta (C. B. Adams) from the Pacific Coast of Panama is quite-close to our species, but there are differences in sculptural details.
Four specimens of this interesting species are known to us.
We are naming this fine species in honor of the late Mr. William G. Fargo, a distinguished engineer and naturalist.