Cassidae with a thin shell, sculptured predominantly with low spiral cords (although weak axial ridgelets are present in some species); most species with flat-crested cords and flat-bottomed interspaces; aperture weakly to moderately callused, terminal varix moderately prominent in many species, completely lacking in a few; anterior siphonal canal very short or represented only by a dorso-ventrally oriented notch in the apertural margin (normal to the coiling axis of the teleoconch), accommodated at the base of the columella by its shortening and deviation to the left. Protoconch relatively large, turbiniform, of about 2.3-3 whorls, with prominent cancellate sculpture. Animal with no obvious, pigmented eyes; proboscis short and wide, length c. twice width; males with a short, wide, dorsoventrally flattened penis with a triangular outline and subquadrate termination. Osphradium curved to weakly S-shaped. Operculum with its nucleus at the anterior end (base) of the right (abaxial) margin, producing spiral initial growth lines (rigiclaudent paucispiral, in the terminology of Checa & Jimenez-Jimenez 1998) that become more obviously commarginal as the operculum grows (rigiclaudent commarginal, in the terminology of Checa & Jimenez-Jimenez 1998). Radula essentially as in Galeodea; the larger species with shorter, more numerous and more closely spaced denticles on the central and lateral teeth (up to 14-20 in the larger species) than in Galeodea (in which the maximum is about 12 denticles).

Anatomical examinations carried out allow a new concept of the genus, and also allow the separation of the new genus Eucorys for two Caribbean species with thicker, more colourful shells and longer anterior siphonal canals than Oocorys species. Oocorys differs from Galeodea in having a thinner, simpler shell with still more predominantly spiral sculpture than Galeodea, with a less well developed anterior canal than that in Galeodea which, instead, is little more than a notch (normal to the coiling axis, i.e., oriented in the dorsoventral plane rather than the anteroposterior plane) in the anterior shell margin, accommodated at the base of the columella by a shortening and deviation to the left of the columellar base, producing a cut off appearance. Most species have a thinner and less well-developed terminal varix than that of most Galeodea species, and some mature specimens of some Oocorys species completely lack a terminal varix. As noted first by Dall (1909), the weakly spiral nuclear area of the operculum also is an important character of Oocorys.