1903.] Hay, North A7tierican Cretaceous Fishes. 3 



that in a specimen of Hypsocormus from Solenhofen, which 

 the writer has been able to examine, there are evidences of 

 the presence of ossified scapula and coracoid. If this shall 

 prove to be the case, the fact that these elements are ossified 

 in ProtosphyrcBna will have no bearing on the question re- 

 garding the presence of vertebrae. 



While there are many interesting and important characters 

 common to Hypsocormus and Protosphyrcena, there are also 

 many striking differences. I regard the deeply socketed 

 teeth of ProtosphyrcBna as furnishing a character of family 

 value. Woodward indeed states that the teeth of Hypso- 

 cormus are in incomplete sockets, those of the dentary of H. 

 tenuirostris (Cat. Foss. Fishes, IV, p. 397) being fused with 

 the bone in sockets which are incomplete on the inner side. 

 The condition of such teeth is certainly very different from 

 that of the teeth of ProtosphyrcBna, which are in complete and 

 very deep sockets. It evidently signifies a great departure 

 from the primitive condition in fishes, when teeth become so 

 deeply implanted in the bone and are replaced, not by new 

 teeth developing in the mucous membrane of the mouth, but 

 from germs lodged deep in sockets. 



The pectoral fin of ProtosphyrcBna is quite different from 

 that of Hypsocormus , as may be seen by comparing the 

 description and figures of P. perniciosa presented in this 

 paper with the description of the fin given by Dr. Wood- 

 ward on page 398 of the work cited above. In ProtosphyrcBna 

 there is no such intimate fusion of rays and the foremost rays 

 are extremely short. 



The condition of the shoulder girdle of ProtosphyrcBna 

 would appear to relegate the genus to the Isospondyli. 

 Whether the possession of a splenial and a slight excess of 

 baseosts is sufficient to exclude it from this order may have 

 to be determined hereafter. At any rate, the genus is close 

 to the border line between the Halecomorphi and the Isos- 

 pondyli. 



Protosphyrsena nitida {Cope). 



Erisichthe nitida Cope (E.D.), Proc. Acad. Nat. Sci. Phila. 1872, p. 

 280; Bull. U. S. Geol. and Geog. Surv. Terrs. I, No. 2, 1874, p. 42; 



