Pentacta

Goldfuss, 1820

18 species

Body with a more or less flattened ventral side with the tube feet arranged in 3 bands. Dorsal side vaulted with feet of different size, often as large papillae, frequently scattered in the interambulacra. Around the base of the introvert and the anus, the ambulacra form thick valves. Tentacles 10 the 2 ventral smaller. Skin rigid, filled with spicules. Calcareous ring simple, posteriorly often strongly undulated but never with posterior prolongations. Spicules consisting of an external layer of either baskets or delicate reticulated bodies, and the inner layer knobbed buttons, heavy plates, or reticulated bodies. Feet apparently with no end plate; walls supported by perforate rods or plates; dorsal papillae with mostly curved supporting plates. Tropical shallow water forms. (Deichmann, 1958)

Body mostly in the mid portion, 4 edged. Mouth closed by 4 flaps: the anus has flaps and teeth. Radii in some varieties have skin growths. In the ventral radii there are feet, in the dorsal radii there are feet or papillae; in a few varieties the ambulacral appendages are situated on hard pointed warts. The interradii are naked or covered with scattered papillae. There are 10 tentacles, the two ventral ones smaller. The calcareous ring is simple, strong, and without forked tail. The calcareous deposits of the skin are in 3 forms: 1) above there are cups or bowls or spiked network plates. 2) strap shaped strong plates with perforations and with bumps; the bumps are often connected by bridges which can broaden to a cover plate to one side or both sides. 3) Large scales, they can consist of two plates which are then connected by means of columns; they can also consist of several layers of network; thereby the net strands can be so thickened that the interval spaces shrink to fine canals. In a few deposits the plates of the second form do not lie in the middle as a second layer but rather between the scales or below them, whereby in the later case they support the often obliquely positioned scales. (Panning, 1971, newly conceived)