Mesothuria

Ludwig, 1894

6 subgenera; 32 attributed species, 27 current

Body often cylindrical, slightly attenuating toward both ends, without marginal fringe. 12 to 20 tentacles, without tentacle ampullae. Dorsal side covered with numerous pedicels, small and equal sized. Mouth terminal. Genital organs only on the left side of the dorsal mesentery. Skin thin. Calcareous deposits tables, no C-shaped spicules. Development unknown. (Mortensen, 1927)

Twenty, rarely 18-19 tentacles; no tentacle ampullae; stone canal attached to body wall without penetrating it; ventral side usually somewhat flattened; dorsal side more or less uniformly covered with small pedicels, which are small and of equal size, or much smaller dorsally, where they are sometimes hardly visible. Single genital tuft, places to the left; anus ventral, or subventral, without special arrangement; calcareous deposits present in the body wall and pedicels developed as tables exclusively, either tri or quadri radiate; no supporting rods in pedicels. (Deichmann, 1930)

There are 6 sub-genera. These are differentiated only by the key presented in the text. (Heding, 1942 )

? triradiata (Heding, 1942 West Africa), but not in Heding 1940 or 42?, in HBF list. (Heding, 1942 )

* Heding divided this genus into 6 subgenera, which have met with little support. In fact, no one has used these subgenera since Hedings original publication. When the family Synallactidae is revised, and the family is in desperate need of revision, the subgenera of Mesothuria are likely to be obliterated. (Heding, 1942 )