DENDROCHIROTA 



573 



Four genera (Cucumaria, Thyone, Phyllophorus, and Psolus) and 

 sixteen species have been recorded from British waters. 



Cucumaria is remarkable for being the only genus of Holo- 

 thuroidea in which 

 the body is penta- 

 gonal in cross- 

 section. In the 

 majority of its 

 species the tube- 

 feet are confined 

 to two rows along 

 each radius, but 

 in a few there are 

 some scattered 

 tube-feet in addi- 

 tion. There are 

 only ten buccal 

 tentacles. The 

 species figured (C. 

 croeea) is an Ant- 

 arctic one which 

 carries the young 

 on the back. 

 Thyone differs in 

 being circular in 

 cross - section and 

 in having the 

 tube-feet scattered 

 evenly over the 

 whole surface. In 

 Fhyllophorus (Fig. 

 260) the tent- 

 acles are more 

 than fifteen, and 

 are disposed in two 

 circles, an inner 

 of smaller and an 

 outer of larger tentacles, 

 scattered. 



Fsolus is a most extraordinary genus. 



The other podia are, as in Thyone, 



There is a well- 



