SALTER ETJRYPTERUS. 81 



On some Species of Eurypterus and Allied Forms. By J. W. 

 Salter, Esq., F.G.S., A.L.S., of the Geological Survey of Great 

 Britain. 



[Eead May 21, 1862.] 



Since the appearance in 1859 of the memoir by Prof. Huxley and 

 myself on Pterygotus and its allies, the great work of Prof. Hall, of 

 Albany, has appeared ('Palaeontology of New York,' vol. iii.), containing 

 the fullest material for the illustration of this genus ; and following, 

 as it did, upon the very full account given by Dr. Wieskowski, 

 it has completed our knowledge of the structure of this remarkable 

 genus. And there seems to be now no doubt whatever that the ano- 

 malous plates and processes about the position of which Prof. Huxley 

 and myself were compelled to guess, and which for many obvious 

 reasons were compared with the under portion of the head, really 

 belong to the under part of the thorax. 



All this was as satisfactorily made out by the Russian author as by 

 Prof. Hall's independent researches. "We had also arrived at the 

 same conclusion before Wieskowski's admirable paper reached us. 

 For previous to the Meeting of the British Association at Aberdeen 

 in 1859, I was sent by the Director- General of the Geological 

 Survey to examine the collections made by Mr. Slimon, of Lesma- 

 hago ; and in that fine series (which was sent to the Meeting for 

 exhibition) we found abundant proofs of the true position of the 

 sternal plates, such as Wieskowski and Hall have figured, and of the 

 place of the post-oral plate, previously assigned by Prof. Huxley to 

 the hinder margin of the mouth. The position of the chelae in these 

 new specimens also confirmed the Professor's judgment in assigning 

 them to the antennae or antennules ; and they supported my own 

 view too as to the existence of three pairs of appendages to the head, 

 exclusive of the chelae and the large swimming-feet, which are also, 

 as we learn from the new and more perfect specimens found both in 

 America and Russia, included with the appendages of the mouth. 



The chief new points, I take it, in Prof. Hall's beautiful series are, 

 first, the larger number of joints in the great maxillary appendages 

 than was supposed from analogy with Pterygotus, where there are 

 certainly only seven ; and secondly, the existence of ocelli on the 

 dorsal surface of the shield, such as give it a wonderfully limuloid 

 aspect. But some of the Copepoda have similar ocelli ; and as to 

 the affinities, it would be out of place in every way to give my 

 opinions, when the naturalist is by who first truly studied these 

 relations. Whatever corrections better specimens may have led to, 

 the main credit is due to him who from fragmentary materials con- 

 structed a true hypothesis. The business of the palaeontologist — 

 half-naturalist, half-geologist — is to collect, arrange, and describe the 

 material, giving to and receiving from both naturalist and geologist 

 all the aid he can. 



The kindness of some friends in Scotland has lately enabled me 

 to examine, for the purpose of description, the rare Crustacea, from 

 the Glasgow coal-field, published in the last volume of the Society's 



VOL. XIX. PART I. G 



