484 ON" CAEB02frFEE0US ENCEINITES. 



the other, and I have a specimen in which this plate is in one case 

 pentagonal. G. calcaratus, also in the British Museum, has the 

 third radial normally heptagonal. 



The British Museum specimens of hursa have the first inter- 

 radial generally pentagonal, but I have three specimens, which I 

 believe to be this species, in which this plate is generally hex- 

 agoDal. There are a considerable number of specimens labelled 

 G. mammillaris in the British Museum, and in all of them this 

 plate is hexagonal. It is quite clear then that these two points must 

 be removed from the generic description. 



Professor McCoy unfortunately gave the name ahnormis to an 

 Irish specimen, which has the third radial heptagonal and first 

 intercostal hexagonal, on the ground that in all others of the 

 genus these plates were pentagonal. His specific characters thus 

 fall to the ground, and the only points in which his description and 

 figure differ from hirsa are, the larger size, the absence of marked 

 depressions at the angles of the plates, and the statement that the 

 proboscis is central. 



The depressions at the angles are not well marked in all specimens 

 of hursa, and therefore I do not attach much importance to this. 

 With regard to the proboscis, I would lemark that no other species 

 of Gilhertsocrinus has a proboscis at all, and that the figure does not 

 prove the existence of one in this case. What McCoy calls the 

 proboscis looks just like a raised mouth at the top of a rather 

 conical dome. In this it much resembles a specimen of Mr. Rofe's 

 in the British Museum, which has a row of nearly vertical plates 

 round the mouth, but which cannot fairly be said to have a proboscis. 

 It is true that hursa has the mouth eccentric, but I cannot help 

 thinking that some fiii'ther proofs are necessary to shew that this is 

 not merely a large specimen of hursa. 



Mr. Eofe writes to me that no reliance can be placed on the 

 number of sides of the plates, especially in the genus Ehodocrinus 

 or Gilbertsoerinus, as they frequently vary on the same specimen. 

 I cannot quite agree with this, as regards the radials, because the 

 specimens shew that hursa has the third normally heptagonal, and 



