

< 



the Morphology of the Blastoidea. 239 



of the same kind appears in the two Belgian species of Oropho- 



cnnus. 



The lateral " ovarian opening " of Hall and Romer has 

 been described as the anus by Zittel*, and, we think, rightly 

 so. Sutures appear to us to proceed from it down the steep 

 walls of the radial sinuses at its sides, towards the ends of the 

 short ambulacra. These sutures thus divide the " coronal 

 process " into an outer portion formed by the limbs of adja- 

 cent radials, and an inner portion formed by an oral plate. 

 The anal opening is between this oral and the two radial 

 limbs against the inner faces of which it rests ; so that it is 

 not confined to an oral plate, as it is in so many Blastoids 

 {Granatocrinus , Pentremites, &c), but occupies its primitive 

 embryonic position between two radials and the corresponding 

 oral. 



Each of the other spiniform processes in the four remaining 

 interradii is similarly divided into an outer part, formed by 

 the contiguous limbs of two adjacent radials, and an inner 

 portion or oral. The calyx of Stephanocrinus thus appears to 

 us to consist of three rows of plates — (1) basals, (2) radials, 

 and (3) orals, just like that of other Blastoids. Romerf 

 thought that he was able to detect the oro-radial sutures, but 

 hesitated to express a decided opinion about them ; and Hall 

 seems to have thought their presence possible in S. angulatus. 

 In his later figures of S> gemmiformis he actually represents a 

 u third range of plates/' which are obviously small orals ; and 

 he speaks of them in S. pulchellus J as u extremely minute, 

 except on the anal (?) side, where the terminal plate broadly 

 truncates the upper sides of the two adjacent plates of the 

 second range;" but his figure is too small to show this pro- 

 perly, as is also that of Messrs. Miller and Dyer§. The 

 Stephanocrinus osgoodensis of the first of these authors || is 

 still too imperfectly known for an opinion to be formed on 



this point. 



The ambulacra of Step hanocr inns are even now but little 

 understood. According to both Hall and Romer the summit 

 of S. angulatus consists of a central " proboscis " of five 

 plates, from which five pairs of linear plates extend along the 

 ambulacra. We have only seen this proboscis in one speci- 

 men, but regard it as a vault of a few plates covering in the 



* Palaontologie, Bd. i. p. 436. 



t Loc. cit. p. 370. 



% Indiana Report, p. 280. 



5 Journ. Cincinn. Soc. Nat, Hist. vol. i. pi. ii. fig. 13. 



|| Ibid. vol. ii. pi. x. fig. 7, 



