HOPLOPARIA. 37 



which genus, at that time, Homarus was not considered distinct. This similarity is 

 particularly striking in the larger London Clay species Hoploparia gammaroides, in which 

 the anterior legs and the abdomen are almost identical in form with Homarus. A closer 

 examination, however, will fully justify Professor M'Coy's separation of these fossils from 

 all the recent forms of Astacidae. The principal and most obvious distinctions are the 

 following. The simple, awl-shaped rostrum, differing from that of Homarus and Nephrons 

 in its not having any armature, and from that of Astacus in its form, which, in the latter, 

 is rather broadly triangular ; the deep cervical furrow terminating abruptly at its internal 

 extremity, without reaching the margin of the carapace. A distinct, bifurcate furrow, 

 called by Professor M'Coy the " X-like cheek-furrow," but to which 1 have given the name 

 of hepatic from its situation, and which does not exist in any recent species of Astacidae 

 that I have seen, excepting, in a much less conspicuous state, in Nephrops Norvegicus, 

 and, as a mere indication, in an undcscribed species of Astacus from Australia. The 

 arched process immediately over the base of the external antennas, the scale of which 

 emerges immediately from beneath it, on which Professor M'Coy so much depended for its 

 distinctive character, is scarcely different in any essential point from the same part in the 

 recent genus Nephrops, as will be seen by referring to the figure of that part which 

 I have given in Plate X, fig. 10. The armature, also, of the same part, upon which 

 the generic name was founded, is equally similar. The extremities of the four pairs 

 of ambulatory feet are wanting in every specimen I have seen of the different fossil 

 species, so that it is impossible to determine whether or not the second and third pairs are 

 didactyle, as in every recent species of the family. The fragments of the antennae, which 

 exist in several specimens in the collections of Mr. Bowerbank and Mr. Wetherell, exhibit 

 a perfect resemblance to those of Homarus. 



There are probably four species of this genus known. One described by Mr. George 

 Sowerby as Astacus longimanus* from the lowest Greensand of Lyme Regis ; another, 

 Hoploparia prism atica,\ described by Professor M'Coy, from the Speeton Clay of Speeton, 

 in Yorkshire; and two, also described by the same author, from the London Clay, 

 H. gammaroides, and H. Belli.% I have not had an opportunity of comparing either the 

 species from Lyme Regis, or that from Speeton, with those of the London Clay, but hope to 

 be able to do so before the completion of the future portion of this work. Mr. Sowerby 's 

 figure of the former exceedingly resembles H. Belli, but is certainly not identical. 



* 'Zool. Journ.,' ii, p. 493, t. xvii. 

 t ' Ann. Nat. Hist.,' 1. c. 



\ ibid. 



