A MONOGRAPH 



OF THE 



BRITISH FOSSIL CRUSTACEA 



OF THE 



Order MEROSTOMATA. 



PART V. 



Sub-Order— XIPHOSURA, Gronovan. 

 Introduction. 



In the first part of this Monograph (p. 24) I have alluded to the proposal made by 

 Professor McCoy, in 1849, 1 to unite in one tribe of the order Entomostraca, the recent 

 and fossil Limulida, and the extinct genera of Pteryyotus, Eurypterus, &c. 



This generalization, however, failed to meet with acceptance and adoption, having 

 been founded upon an incorrect view of the structure of the fossil forms it associated 

 together. 2 Nor can it be doubted that the arrangement was based on conjecture rather 

 than upon a minute acquaintance with the anatomy of those extinct genera Pteryyotus 

 and Eurypterus, then only known in England by extremely fragmentary remains. 3 



In the important memoir by Messrs. Huxley and Salter, published in 1859, 

 Professor Huxley thus expressed his views on the union of the two groups : 



" The Pcecilopoda are, I believe, the only Crustacea which possess antennary organs 

 like those of Pteryyotus, and, like them, have the gnathites converted into locomotive 



1 See 'Ann. and Mag. Nat. Hist.,' 2nd series (1849), vol. iv, p. 393, and Lyell's 'Manual,' 1855, 

 5th edition, p. 420. 



2 See Introduction to Huxley and Salter's 'Monograph on the Eurypteridse,' 1859, p. 7, and 

 H. Woodward's paper " On the Structure of the Xiphosura having reference to their Relationship with the 

 Eurypterida," 'Quart. Journ. Geol. Soc.,' 1867, vol. xxiii, p. 28. 



3 See McCoy's restoration of Pterygotus (reproduced from Lyell's * Manual '), Part I, p. 24, of this 

 Monograph. 



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