﻿26 BRITISH FOSSIL CRUSTACEA. 



of posterior long gnathites, with a large toothed coxopodite, succeeded by a number of 

 joints, the last of which has the form of an oval palette. These last members probably 

 performed the function of locomotive or swimming feet. A considerable epistomial 

 region lies in front of the mouth, as in Limulus, and a large oval plate, emarginate 

 anteriorly, covered the mouth in the median line. 



" No limbs have been found in connection with the abdominal somites, nor have any 

 detached parts different from those just described been as yet discovered. Many parts of 

 the surface of the body and of the appendages exhibit an exceedingly peculiar structure, 

 resembling the conventional representation of feathers, or the mode in which they are 

 represented in the Assyrian and Egyptian sculptures ; and it was from this cause, appa- 

 rently, that the Scotch quarrymen conferred the title of ' Seraphim' upon the Pterygotus. 



" The Diastylida are the only Crustacea with which I am acquainted which exhibit 

 anything similar to this ornamentation ; and in the number of free somites, and the more 

 or less rudimentary condition of the abdominal appendages, this aberrant group of 

 Podophthalmia presents other analogies with the Eurypterida. The carapace, the pre- 

 hensile antennas, the largely developed posterior gnathites of Pterygotus, are to be 

 paralleled among the Copepoda and Xiphosura, from which, however, and indeed from all 

 other adult Crustacea with which I am acquainted, the Eurypterida differ widely in 

 certain other respects. 



" The absence of developed posterior thoracic and abdominal members in a Crustacean 

 possessing the corresponding somites is to be met with, in fact, only among the Zoseiform 

 larvae of the Macrura and Brachyura, in which, as we have seen, the proportions of the 

 body are not dissimilar to those of the Eurypterida, where the abdominal appendages are 

 entirely absent, and the well-developed and conspicuous thoracic and cephalic members 

 are not more than two or three pairs in number, and consist of antennas and maxillipedes, 

 the latter serving as locomotive organs. 



" I conceive, therefore, that the Eurypterida must form a group by themselves, which 

 are best understood by combining together organic peculiarities at present found only in 

 the Copepoda, the Xiphosura, the Biastylida, and the larvae of PodopJdhahnia." 



41. In June, 1858, 47 Mr. J. W. Salter communicated to the Geological Society 

 descriptions and figures of six new species of Eurypterus, and gave an account of the dis- 

 tribution of the group. 



42. On the 22nd January, 18 59,^ appeared Messrs. Huxley and Salter's grand 

 Monograph ' On the Anatomy and Affinities of the Genus Pterygotus,' with descriptions 

 of twelve species (pp. 105, 8vo, and sixteen folio plates).* 



43. In the same year a Russian naturalist, Dr. Johannes Nieszkowski,! published 



* This standard work will necessarily be so frequently referred to in the pages of this Monograph, that 

 it would be superfluous to give a mere extract from it here. Its authors are quoted in clauses 26, 36, 37, 

 40, 41, 45, 51, and 57. 



+ Dr. Nieszkowski's paper is referred to by Mr. Salter, ' Quart. Journ. Geol. Soc.,' 1863, vol. xix, p. 81 ; 

 but the author's name is misprinted Wieskowski. 



