NO. 3 deichmann: holothurioidea; part i, dendrochirota 71 



Order DENDROCHIROTA 



Diagnosis. — Plankton feeding holothurians with dendritic tentacles, 

 rarely fingerlike; number var>'ing from 10, the 2 ventral often smaller, 

 in some cases less than 10, or 12-20, up to 30 in a few genera. Feet ar- 

 ranged along the ambulacra or also scattered in the interambulacra ; ter- 

 minal and dorsal ones often modified into papillae. 



Internally a calcareous ring, simple, or complex, with shorter or 

 longer posterior prolongations. One or more stone canals, one or more 

 Polian vesicles; usually a well-developed muscle stomach; intestine with 

 the 3 loops attached by mesenteries ; that of the third loop may run along 

 the right or the left side of the midventral muscle band. Retractor muscles 

 well developed, distinctly separated from the longitudinal muscles. Re- 

 spiratory trees mostly well developed, usually attached to the lateral inter- 

 ambulacra. Gonads forming 2 tufts with a shorter or longer genital 

 stolon, and shorter or longer tubes, usually divided near the base. 



Spicules tables, cups, buttons, or plates, et cetera, in some cases large 

 scales covering the entire body, or the dorsal side and the ends. Feet with 

 large end plate, or a vestige, or end plate completely reduced. Tentacles 

 with larger or smaller plates or rods, often rosettes, or no spicules at all. 

 In many forms the spicules disappear normally with advancing age, partly 

 or completely. 



Remarks. — The order seems to be comparatively young. The members 

 occur with few exceptions in shallow water and the distribution of the 

 individual species is rather restricted aside from the deepwater forms and 

 certain Arctic and Antarctic forms. 



Key to the Families of Dendrochirota 



1. Part of the ventral side developed as a thin-walled creeping sole. 



III. Psolidae p. 135 



1. No part of the ventral side developed as a thin- walled creeping sole. 

 II. 



2. Tentacles 10 in number or less I. Cucumariidae p. 76 



2. Tentacles more than 10 in number (12-20, 30). 



II. Phyllophoridae p. 122 



Remarks. — The old division of dekachirote and polychirote forms, 

 designating those with 10 tentacles (or less) and those with more than 

 10, has been abandoned, as it is completely artificial. 



