184 A HISTORY OF EECENT CRUSTACEA 



on account of the contradictions in different writers in 

 regard to the third maxillipeds of Callianassa, some call- 

 ing them pediform, others operouliform. In Cheramus 

 they are distinguished as pediform, but it seems rash to 

 establish a new genus on the very character which some 

 authors ascribe to the old one, especially as Callianassa is 

 not unrepresented in England, France, and the Mediterra- 

 nean, and specimens might have been examined to clear 

 up the disputed point. In the British Museum Leach's 

 type-specimens of Callianassa suhterranea, from Bangs- 

 bridge in South Devon (Salcombe at the mouth of the 

 Eangsbridge estuary being probably intended), have third 

 maxillipeds that might well be described as pediform. 

 But other specimens at the same museum, which have 

 been labelled as belonging to the same species, were 

 shown me by Mr. Pocock, and in these, which came from 

 Jersey, the third and fourth joints of the maxillipeds in 

 question are greatly expanded, quite deserving the name 

 operculiforra . But these specimens also have a more 

 quadrate telson than those from Devonshire, and are 

 doubtless quite distinct. Since, however, in the type of 

 Callianassa the maxillipeds are pediform, the chief reason 

 for the institution of Cheramus is cut away. Its name 

 signifies ' a gap,' but it has not succeeded in filling one. 



Callianidea, Milne-Edwards, 1837, closely resembles 

 Callianassa, but with some differences in the branchial 

 arrangements, and, besides having the second pleopods 

 like the following three pairs, in all these pleopods ' the 

 margins, instead of being fringed with small hairs or cilia, 

 have these modified into soft and flexible articulated mem- 

 branous filaments.' Milne-Edwards supposed that these 

 were true branchial appendages, and that a link was thus 

 established between this family and the Squillidse in the 

 sub-order Stomatopoda. With his own genus he coupled 

 Guerin's Isea. But Mr. Spence Bate regards it as pro- 

 bable that Gugrin's genus was founded on a damaged 

 specimen of Callianidea, and with some reason thinks that 

 the fringed pleopods of that genus cannot be regarded as 

 branchial for purposes of classification. 



