l ir> 



FOSSIL FISHES OF THE ENGLISH CHALK. 



;ill the principal teeth much compressed, with sharp 

 anterior and posterior edges, and fixed in deep, 

 complete sockets; those of the vomer, premaxilla, 

 and splenial especially large, and similar teeth pro- 

 jecting forwards from the downwardly-curved 

 anterior end of the oral border of the den tar y ; 

 those of the maxilla and hinder portion of dentary 

 comparatively small and in a single close series. 

 Gular plate present, and short branchiostegal rays 

 very numerous. Pectoral fins large and sickle- 

 shaped, consisting of closely-apposed, unjointed and 

 unbranched rays, of which the majority terminate 

 successively at the oblique, trenchant anterior 

 margin. 



Type Species. — Protosjiliyrxna fero.v, from the 

 English Chalk. 



Remarks. — The remains of this genus were first 

 discovered in the English Chalk. The teeth were 

 originally referred by Agassiz 1 in error to Sauro- 

 cephalus of Harlan, 2 while the pectoral fins were 

 wrongly described as fin-rays of the Elasmobranch, 

 Ptychodus. 8 The mistake in the identification of 

 the teeth was first pointed out by Leidy {Joe. cit., 

 1857), who, however, failed to recognise that the 

 elongated rostrum belonged to the same fish as 

 these fossils. The pectoral fin-rays were first 

 proved to be not Elasmobranch by Cope (loc. cit., 

 1875), and their identity with Protosphiirsena was 

 subsequently determined both by Cope 4 and by 

 Crook. 5 The head, pectoral arch, and pectoral 

 fins (Text-fig. 43) are now comparatively well 

 known by specimens from the Chalk of Kansas, 



1 L. Agassiz, Poiss. Foss., Feuill, 1835, p. 55. 



2 E. Harlan, Journ. Acad. Nat. Sci. Philad., vol. iii (1824), 

 p. 337. 



3 L. Agassiz, Poiss. Foss., vol. iii (1837), p. 56. 



* E. D. Cope, in A. S. Woodward, Proc. Geol. Assoc, vol. x 

 (1888), p. 321. 



5 A. R. Crook, Palseontographica, vol. xxxix (1892), p. 110. 



Fig. 43. — Protosphynena perniciosa (Cope) ; pectoral fin, about one 

 quarter nat. size. — Upper Cretaceous (Niobrara Group) ; Kansas, 

 U.S.A. Charles H. Sternberg Collection (B. M. no. P. 10340). 



