26 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Nov. 21, 



3. On some new Crustacea from the Uppermost Silurian 

 Rocks. By J. W. Salter, Esq., F.G.S. With a Note on the 

 Structure and Affinities of Himantopterus. By T. H. 

 Huxley, Esq., F.R.S. 



The occurrence of large Crustacea other than Trilobites in the older 

 Palaeozoic rocks is so rare, that we are scarcely prepared for the 

 simultaneous discovery of five or six new forms, of dimensions 

 equalling those of the crabs and lobsters of the present day. 



Except the large Pterygotus of the Tilestone beds, and the Cera- 

 tiocaris from Westmoreland, scarcely any remains of these have yet 

 been made out in Britain. But there have been sundry indications 

 in the occurrence of large tail-spines and fragmentary carapaces, all of 

 which have been most carefully treasured up to wait for further evi- 

 dence, such as that now aiforded by the discoveries of Mr. Slimon*. 

 His admirable collection not only fully explains the meaning of 

 much that was fragmentary before, as in the case of the Ceratiocaris, 

 but gives us new forms of a group of which we knew very little, 

 except that it contained the gigantic Eurypterus of De Kay and 

 the Pterygotus of Agassiz, and was doubtfully referable to the 

 Poecilopoda. 



Of the affinities of the Eurypteridae I am not called upon to say 

 much here, as we hope to fully describe these specimens in the pub- 

 lications of the Survey. The family has been regarded as a group 

 of the Palceadce by Burmeister ; but their relation to the Trilobites 

 seems more than doubtful. Since then Ferd. Romerf has suggested 

 their affinity with Limulus, pointing out, however, the great differ- 

 ences in the feet. Prof. M*Coy has adopted this view, and united 

 Pterygotus and Eurypterus in the family Eurypteridcs, Burm., the 

 principal character of which, as distinguished from the Limuli, is the 

 very obvious one of the free-jointed rings of the abdomen. And in 

 this association I should have been content to leave them, but for 

 the suggestion of a much more complete affinity by Mr. Huxley, 

 which will, I think, when he has worked it out for us, explain not 

 only these forms, but also the group of Ceratiocaris and its allies 

 above mentioned, which are far from uncommon in the Ludlow rocks. 

 And it may, perhaps, include my Cambrian genus Hymenocaris, and 

 thus relieve the Phyllopoda from the burden of these old and ano- 

 malous Palaeozoic forms. As Mr. Huxley has promised to add a full 

 note upon the subject, I will not enter further into it here. 



The beautiful figure by Ferd. Romer of the Eurypterus remipeSy 

 and Eichwald's late discovery of the E. tetragonophthalmus in the 

 Isle of Oesel^:, have furnished good materials for understanding that 

 genus. The latter zoologist especially has been enabled to figure 

 clearly the jointed feet and the sculpture of the rings of the body. 

 And this sculpture is so exactly that of Pterygotus on a small scale, 



* See the preceding paper, p. 15. 

 t Palaeontographica, vol. i. p. 193. 

 + Bulletin de la Soc. Imp. des Naturalistes de Moscou, 1854, no. 1. p. 100. pi. 1. 



