POTERIOCRINID,a:— POTERIOCRINUS. 89 



inches in diameter. This crinoid therefore, with a body apparently so disproportionate 

 to tiie length of its rays, could form by their expansion a net-like apparatus around it 

 to a circumference of nearly twenty inches, or upwards of half a yard. 



This Poteriocrinus has been the cause of much perplexity to Palteontologists. It 

 was first figured by Mr. Cumberland in the Transactions of the Geological Society, but 

 without any specific name being attached to it. Miller appears to have borrowed its 

 fine set of rays to graft on to his restored figure of the Cyathocriniis planus. Dr.Mantell 

 has also figured it under the same name in his instructive work, " The Wonders of 

 Geology;" and we were at one time in doubt as to its true character, but on a careful 

 examination and comparison with a very great number of specimens, we have arrived 

 at the conclusion, that it is a true Poteriocrinus, and as such we do not hesitate to place 

 it in that genus. It should never have been confounded with the C planus, or mistaken 

 for any other species of Ci/athocrinus, because no crinoid belonging to that genus has 

 the rays attached by the whole breadth of the ray bearing plates as they do in the fossil 

 which has caused so many errors as to the true position it should occupy among the 

 Crinoidea. 



If the fossil which Mr.McCoy has named Cyathocriniis macrocheirus, be really Identical 

 with the P. longidactijlus as we suspect it is, then the column is clearly pentagonal. But 

 whether we are correct in our conjecture or otherwise, it is certain that the fossil 

 in question cannot be a Cyathocrinus, because, as before observed, in none of that genus 

 do the rays articulate in the manner represented in Mr. McCoy's figure. 



1.5. Species. Poteriocrinus abbreviatus. (Austin.) 

 PI. 11. Jiff. 4 a. 



Definition.— The dorso-central plates agree in number and arrangement with the 

 typical species, but they are comparatively much shorter; rays twenty? column circular, 

 and at the summit composed of alternate thick and thin joints. 



Synonymes and References. 

 Cladocrinites brevidactylus.— Messrs. Aust. Ann. .^ Maff. N. Hist. vol. 1 1, yj. 198 



