90 



THE ATLANTIC. 



[chap. II. 



and the junctions in the mature animal are somewhat obscure. 

 The second tier consists of iive radials, which 

 are thin, broad, and spade -shaped, with a 

 slight blunt ridge running up the centre and 

 ending in a narrow articulating sufrace for an 

 almost cylindrical first brachial. The arms 

 are five in number ; they consist of long cy- 

 lindrical joints deeply grooved and inter- 

 sected by syzygial junctions. The first three 

 joints in each arm consist each of two parts 

 separated by a syzygy ; the third joint bears 

 at its distal end an articulating surface, from 

 which a pinnule springs. The fourth arm- 

 joint is intersected by tw^o syzygies, and thus 

 consists of three parts, and so do all the suc- 

 ceeding joints; and each joint gives off a 

 pinnule from its distal end, the pinnules 

 arising from either side of the arm alter- 

 nately. 



The proximal pinnules are very long, run- 

 ning on nearly to the end of the arm, and 

 the succeeding pinnules are gradually shorter, 

 all of them, however, running out nearly to 

 the end of the arm, so that distally the ends 

 of the five arms and of all the pinnules meet 

 nearly on a level. This is an arrangement 

 hitherto entirely unknown in recent crinoids, 

 although we have something very close to it 

 in some species of the paleozoic genera Po- 

 FiG. <i5.—uijocrinus Be- teriocvinus End Cyathocrinus. Here I be- 



thellianus. About four ■,. ■• , i -, ^ i , tt 



times the natural size. liGvc, howcver, the resemblancc betw^een Jii/- 



(Station cxLvii.) ocrinus and the early fossil forms ends. The 



outer part of the disk is paved w^ith plates irregular in form and 



closely set. Bound the mouth there are five very strong and 



