592 



ECHINODERMATA — CRINOIDEA 



Fig. 271. — Pentacrinus asteria. X J. (From 

 Wyville Thomson. ) 



radial bears a pinnule. 

 Pentacrinus is found in: 

 both the Caribbean Sea 

 and the Pacific Ocean ; 

 Metacrinus in the Pacific. 

 It appears that the Pen- 

 tacrinidae when young 

 are attached by a foot- 

 plate at the apex of the 

 stem ; but when adult, 

 the stem is broken in 

 two and the animals, 

 like Antedon, swim by 

 movements of the arms, 

 dragging a large part of 

 the stem after them, by 

 which they effect tem- 

 porary attachment. As 

 in other stalked forms, 

 the cavities of the 

 chambered organ are 

 prolonged into canals 

 which traverse the stalk ; 

 but in this family there 

 is the peculiarity that a 

 repetition of the cham- 

 bered organ is found 

 opposite every whorl of 

 cirri. 



Fam. 4. Holopodidae. 

 — Stem represented by 

 a leathery noncalcified 

 outgrowth from the base 

 of the calyx ; one circle 

 of radials indistinguish- 

 ably fused with the 

 basals and with each 

 other to form the walls 

 of the calyx. Large 

 oral plates, ten short 



