BRITISH FOSSILS. 



PLATE I. FIG. 17. 



EUBYPTERUS LANCEOLATUS. 



GEN. CHAR.* ETJRYPTERUS, Dekay, 1826. Body as in Pterygotus, with 

 12 segments, eyes subcentral, antennae without chelae. 



E. elongatus, postice attenuates, articulis 12, quorum 10 transversis, 

 pemdtimo oblongo ; caudd acuta producta, ad basin tumida. 



SYNONYM. Himantopterus lanceolatus, SALTER, in Quart. Journ. Geol. 

 fe'oc., 1. c., p. 28, fig. 5 (tail joint). 



Perfect, except the carapace, which, when the plate was engraved, 

 was supposed to have resembled that of P. acuminatus. It is, 

 however, almost certainly an Eurypterus, from the elongate-linear 

 caudal joint, but the shape of the swimming feet is more linear 

 than usual in the genus. It is here figured because of its associa- 

 tion with the Pterygoti in my former notice. 



Body two and a half inches long, by three-quarters wide in the 

 broadest part, which is about the fourth segment ; from thence it 

 tapers very gradually to the last. The anterior segment is narrow 

 (short), not above one-fifth as long as wide, with its ends recurved ; 

 the next, not much broader, is straight posteriorly. The last thoracic 

 ring (sixth) is three and a half times as wide as long, with the 

 posterior angles a little produced ; from thence the joints are larger 

 and less transverse, the tenth being onty half as wide again as long. 

 The penultimate joint is about as long as wide, but narrowed 

 posteriorly. 



The terminal joint (telson) is three-quarters of an inch long and 

 only two-tenths wide ; it is regularly conical and acute, has a 

 median keel (apparently tumid at the extreme base) nearly all the 

 way down, and also one along each edge. 



* For remarks on the generic character of Eurypterus, see pp. 35. 38. It differs 

 from Pterygotus chiefly in the subcentral eyes, but also by the want of the large chelai 

 to the antennae. 



It is hoped to illustrate this genus in a future monograph, meanwhile the reader is 

 referred to the Quart. Journ. Geol. Soc., vol. xv., for information on the species. 

 [1. E 



