Seguenziids are trochiform gastropods that range from 2 mm to 22 mm in maximum dimension. They occur throughout the Pacific, Atlantic, Indian, and Antarctic oceans, and attain maximum diversity at bathyal and abyssal depths (i.e., below 1000 m) where they are a characteristic component of the fauna. Very few species have been recorded at depths less than 300 m, and there are no intertidal representatives. The shells are notable for exquisite sculpture and elegant shape, and are generally thin, translucent, nacreous, and white. They often bear a distinctive, tooth-like fold on the inner lip. With the exception of species of Guttula Schepman, which have highly simplified shells, all are rendered particularly distinctive by the presence of 1-3 concave notches in the outer lip. The radula is of a reduced rhipidoglossate type (Bandel 1979), which resembles that of archaeogastropods in having more than 2 pairs of marginal teeth yet resembles that of mesogastropods in having only a single pair of lateral teeth. The operculum is chitinous and multispiral as in Trochoidea, but often tends to be more loosely coiled, with fewer whorls. The radula morphology and the presence of a well developed
penis, a fully monopectinate ctenidium (McLean 1981), a monotocardian circulatory system, and other anatomical features (Quinn 1983) indicate that the group has independently approached or acquired some of the character states known from mesogastropods. Judging from the stomach contents of all the present species that were taken alive, seguenziids feed on foraminifera.