HOLOTHUROIDEA. 



267 



canal is single and usually joins the body-wall. Neither of the respiratory 

 trees are connected with the vascular network of the intestine. Abyssal 

 forms. Synallactes Luclw. Meseres Ludw. Bathyplotes Oest. Bathyher- 

 pystikes Sluiter. Benthothuria R. Perrier. Pseudostichopus Theel. 

 Mesothuria Ludw. Paelopatides Theel. Zygothuria R. Per. 



Fam. 3. Elasipodidae. Mouth more or less ventral. Ventral surface 

 usually flattened toasolelike surface with 

 three rows of feet (trivium). With 10, 

 15 or 20 more or less shield-shaped tenta- 

 cles, without ampullae. Calcareous ring 

 of 5 radial pieces or of 5 radial and 5 inter- 

 radial complete or incomplete pieces. 

 Otocysts generally present on the radial 

 nerves. Stone-canal attached to the skin 

 and often opening to exterior. Longi- 

 tudinal muscles simple, retractors absent. 

 Respiratory trees absent or vestigial. 

 Cuvierian organs absent. For the most 

 part abyssal. 



Sub-fam. 1. Deimatinae. Body 

 generally elongated. Calcareous ring 

 well developed. Ventral surface flat- 

 tened, the unpaired radius being with- 

 out or with reduced feet. Tube-feet 

 serially arranged. Deima Theel (Fig. 

 184). Oneirophanta, Orphnurgus, Laet- 

 mogone, Iliodaemon, and Pannychia 

 Theel. Scotodeima, Laetmophasma, 

 and Capheira Ludwig. Benthogone 

 Koehler. 



Sub-fam. 2. Elpidiinae. Usually 

 with 10 tentacles. Ventral surface 

 flattened, the unpaired radius being 

 always without feet. The dorsal 

 ambulatory appendages much re- 

 duced in number and the latero- 

 ventral feet are frequently confined 

 to the hinder part of their radii. 

 The calcareous ring is without the 

 interradial pieces. Peniagone Theel. 

 Elpidia and Parelpidia Theel. Irpa 

 and Kolga Dan. and Ivor. Scoto- 

 planes, Achlyonice, Scotoannassa, and 

 Enypniastes Theel. Rhipidothuria 

 Herouard. 



Sub-fam. 3. Psychropotinae. With 

 paired ventral ambulacrum with two 



The dorsal ambulacra with papillae all along their length or only in 

 front. A large appendage sometimes projects from the hinder part 

 of the dorsal surface. Calcareous ring with 5 separate calcareous 

 pieces. Benthodytes, Euphronides, Psychropotes (Fig. 185), Psychro- 

 trephes Theel. 

 Fam. 4. Pelagothuriidae. Pelagic forms of medusa-like appearance. 



J 



FIG. 185. Psyc/iru/ititi's Imnji- 

 caiicla (from Lang, after Theeli. 

 1 oral tentacles, 2 mouth, 3, i, S, 

 ambulacral appendages of the 

 trivium (adult-ventral) ; 5 anus ; 

 6 dorsal appendage with its two 

 posterior processes (7). 



10 to 20 tentacles. Un- 

 rows of feet, rarely naked. 



