the Morphologrj of the Blastoidea. 241 



of tlie radial, the lower margin of the side plate above, and the 

 upper oblique margin of the outer side plate, and are, roughly 

 speaking, triangular in shape. The result of this is that the 

 pores are excavated wholly in the outer side plates ; but in G. 

 ellipticus a slightly different arrangement is met with. Here 

 the pores are excavated out of the side plates themselves, the 

 upper edge of the outer side plates being quite straight and not 

 at all cut into. In G. campanulatus the pores are scarcely 

 excavated in the ambulacral plates at all, but are almost wholly 

 so in the edges of the radial plates. There also appear to be 

 slight modifications in the arrangement of the sockets placed 

 on the side plates. In G. orbicularis they terminate narrow 

 grooves which arise from the lower sutures between the side 

 plates and the outer side plates, running almost straight on to 

 the centre of each side plate. There is a similar structure in 

 G. elongatus^ a somewhat aberrant form, which will probably 

 have to be referred to the present genus. Bat in G. ellipti- 

 cus the groove communicating with the socket arises from 

 the suture separating the side plates themselves, and must 

 have been in direct communication with the pore. 



We have come to the conclusion that in Granatocrinus, as 

 understood by us, there is no under lancet-plate, as there is 

 in Peutremites and Orophocrinus ; and we are glad to find our- 

 selves in accord with Messrs. Wachsmuth and Springer on 

 this point *. 



In Granatocrinus the hydrospires are few in number. G. 

 Norivoodi possesses two on each side of an ambulacrum, 

 whilst G. campanulatus, G. orbicularisj G. ellip)ticus, and 

 G. derhiensis have only one each. The abnormal species G. 

 elongatus, to which we shall refer further on, possesses three 

 on each side. 



The central aperture and spiracles in the type species G. 

 Norivoodi, as originally pointed out by Messrs. Owen and 

 Shumard, are closed by a conical integument of small plates f; 

 but our researches amongst the British species have not 

 rewarded us by the discovery of a similar feature. Through 

 the disinterested kindness, however, of Mr. Charles Wachs- 

 muth we have been afforded the opportunity of examining 

 some fine examples of G. Nortooodi in that condition. It has 

 also been pointed out by Dr. C. A. White that in the same 

 species this plated integument passes down and covers the 

 central food- groove of the ambulacra %• 



* ' Revision,' pt. 2, t. xx. f . 6. 



t Joum. Acad. Nat. Sciences Pliiladelpliia, 18-jO, ii. pt. 1, p. Go; also 

 see Shumard, in Swallow's Missouri Geol. Report, \6bb, p. 186. 



X Boston Journal, I.e. p. 484; see also Meek and Worthen, Proc. Acad. 



Nat. Sciences Philadelphia, 1809, p. 8-3. 



