BUFFALO SOCIETY OF NATURAL SCIENCES 



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species than to any other. There remain the specimens of Pterygotus 

 osiliensis and its variety, laticauda. 



In the lower beds of the Old Red sandstone are two species of 

 Pterygotus, bilobus and anglicus to both of which P. osiliensis shows 

 some similarity, though the stronger affinity is to the latter of the 

 two- from Great Britain. A comparison of Schmidt's restoration 

 of P. osiliensis and of an actual specimen of P. bilobus var. inornatus 



Fig. 2 2 a. Pteryogotus osiliensis Schmidt. Restoration 



(After Schmidt. 1883, p. 72, fig. 1 A) 



Fig. 22B. Pterygotus bilobus var. inornatus (Salter). X 



(After H. Woodward. 1878, pi. X, fig. 1) 



Fig. 22c. Chela of Same Species. Xf. 



(Ibid. fig. 2) 



(fig. 22), brings out the similarity in general form, the correspondence 

 of the telsons especially in their bilobate character, the agreement 

 between the pincers and the arrangement of teeth in the chelae, the 

 similarity in the shape of the carapace and in the size and form of the 

 swimming paddles. The abdomen of P. bilobus is not so narrow nor 

 so gracefully tapering as is that of P. osiliensis; the proportions of the 

 carapace likewise differ, that of the former species being longer than 



