van der Spoel and Troost, 1972
Shell moderately small (3 mm maximal diameter), light yellow-brown color, and brown inside the outer lip. Spire of 5 and 1/2 whorls, suture very shallow and difficult to distinguish in side view. Keel tall and rounded. Ridge on underside of spire strongly developed; area between this and umbilicus flattened. Internal structure like that described for A. inclinata, but hardly visible because of the much more strongly developed surface sculpture. Spire whorls with tubercula arranged in distinct spiral lines, which occasionally are elevated sufficiently to almost form spiral ridges. Radula small and ribbon-like (growth angle about 9°). Lateral tooth with an accessory cusp.
It is clear that the two species in this group are closely related, twin species. One could debate whether such species should be taken as subspecies, but this would not resolve the underlying taxonomic problems. On the other hand, it is quite clear that the two species in the A. gibbosa species group, both of which have calcified inner spire whorls and a radula with a very different shape, cannot belong in this group.
See the family Atlantidae for a discussion of the species groups.