Plesiocolochirus

Cherbonnier, 1946

1 species

Body form intermediate between Pentacta and Thyone, resembling the former in the 5 oral valves, but lacking the firm body wall with its 3 characteristic layers of calcareous deposits and its tendency to a quadrangular form. The resemblance to Thyone is in the pliable body wall, with numerous pedicels all over the body, not in longitudinal series. From both genera Apentacta differs in the presence of a longitudinal series of 3-7 or more conical, more or less calcareous, processes on each side of the body. (Clark, 1946, for Apentacta)

Body rigid and pine cone shaped, dorsally curved in. 10 tentacles, the two ventral ones smaller. Mouth is terminal and has five large flaps. On the ventral side there are feet in the radii and interradii, but they are elevated in the radii because of row placement. On the dorsal side there are papillae. The lateral ventral radii have 3-12 large conical growths each with a papilla on the tip. The anal region has small overlapping scales. The anus has 5-10 small teeth. The calcareous ring is well-developed; the posterior radialia have 2 rather long extensions. The middle ventral radialia and the 2 neighboring interradialia are often regressive. The posterior extensions are lacking in the middle ventral radials. In the surface of the skin, there are large flat cups with a distinct primary cross; under that there are large irregular plates with 4-12 perforations and large round bumps and large scales composed of several layers of network. In the feet there are large rods as well as small ones with 2-3 arms, which are perforated on the ends. (Panning, 1949)