ECHINODERMATA : CRINOIDEA. 



213 



late remarkable researches into the life of the deeper parts of 

 the ocean have brought to life several new Crinoids, which will 

 doubtless, when fully investigated, still further fill up the in- 

 terval between the living and extinct Crinoidea. Amongst 

 these may be mentioned Pentacrinus Wyville-Thomsoni, Bathy- 

 crinus gradlis, and Hyocrinus Bethellianus. 



In the second type of the Crinoidea represented in our seas 

 by the forms which are commonly known as " Feather-stars," 

 and which are grouped together under the general name of 

 Comatula the animal is not permanently fixed, but is only 

 attached by a stalk when young. Taking the British Comatula 

 (Antedon) rosacea as the type of this group, the larva, after 

 various preliminary embryonic changes, appears as a small 

 stalked Crinoid (fig. 105, b), in which state it was described as 

 a distinct species under the name of Pentacrinus Europaus. 





Fig. 105. Crinoidea. Comatula (Anterior?) rosacea, the Feather-star, a Free 

 adult; b Fixed young. (After Forbes.) 



In its adult condition, however, the Comatula (fig. 105, a) is 

 free, and consists of a pentagonal disc, which gives origin to 

 ten slender arms, which are fringed with many marginal 

 pinnulse. The mouth and anus are on the ventral surface of 

 the disc, which in this case is again the inferior surface, since 



