Shell of average size for genus, thin, globose and inflated, with rounded shoulder and sides; spire slightly elevated, with rounded whorls; subsutural area slightly flattened; umbilicus present, narrow, deeply perforate; anterior end of umbilicus with single large, prominent raised cord; columellar area with large, prominent, roughly-rectangular parietal shield along posterior one-third of aperture; white parietal shield adherent, extending onto body whorl; anterior two-thirds of parietal shield thin, bladelike, not adherent, with large indented area that exposes entire umbilical opening; edge of indented area with large dark brown stain; aperture wide, flaring, roughly semicircular; shell color dark tan or brown, with pure white anterior end of body whorl and base of shell; interior of umbilicus white or pale tan, with anterior umbilical cord being darker tan; interior of aperture dark tan or brown on posterior area, turning white on anterior area.

Euspira massieri is most similar to the widespread Eastern Atlantic Euspira fusca (Blainville, 1825), which ranges from the North Sea (Faroe Islands) south to Angola. The new Namibian endemic species differs from its wide-ranging congener in having a narrower and more laterally-compressed shell outline, in having a proportionally smaller and narrower umbilicus, in having a prominent anterior umbilical cord, and in having the entire anterior end of the body whorl and shell base being pure white. The most conspicuous difference between E. massieri and E. fusca is seen in the form and structure of the parietal shield along the columellar side of the aperture. In the new species, the parietal shield is proportionall small and covers only around one-third of the parietal area, and extends onto the body whorl as a large white rectangular callus-like structure at the posterior end of the aperture. In E. fusca, the parietal shield is much better developed, extending over two-thirds of the length of the aperture and partially closes off the umbilicus. Although being proportionally larger and better-developed, the parietal shield structure of E. fusca does not have a large, adherent callus-like structure at the posterior end of the columellar area. This large white rectangular callus is unique to E. massieri.

At present, known only from the coast of Namibia, from south of Walvis Bay to Luderitz.
Ecology. The new species prefers organic-rich mud sea floors at depths of around 300 m. Here, it occurs along with other Namibian endemic gastropods such as the aporrhaid Aporrhais pesgallina, and the volutes Athleta massieri and Athleta easoni. For more details on the structure of the deep water Namibian ecosystems, see Petuch and Berschauer.