1903. 



Ha\, North A»ierican Cretaceous Fishes. 



23 



vom.%--' 



had become filled up with bone. His explanation is probably 

 the correct one. At the hinder end of the specimen, on the 

 under side, is a triangular depression. This appears to be 

 produced by the 

 parting of the hinder 

 ends of the vomers, 

 so as to .expose the 

 parasphenoid (Fig. 

 13, par.); but the 

 bones are somewhat 

 eroded. The apex 

 of this depression is 

 considerably farther 

 behind the alveoli 

 of the vomerine 

 fangs than in any 

 other described 

 species of the genus, 

 being about 25 mm. ; 

 while in the type of 

 P. penetrans the in- 

 terval is only 1 5 mm. 



On each side of 

 the basal half of the specimen and extending forward to a line 

 crossing just in front of the vomerine alveoli is a longitudinal 

 excavation. Cope regarded these as probably intended for 

 the reception of the forward prolongations of the premaxillas. 

 It is more probable that they receive the anterior ends of 

 those bones which Felix has called "ethmoidea lateralia." 

 There is some reason to think that a portion of these bones 

 is yet in these excavations. Possibly if the whole of these 

 lateral ethmoids were present the lower surface of the beak 

 would not be so constricted as it is. 



The hinder end of the upper surface is occupied by a tri- 

 angular smooth depression (Fig. 14, jr.). The writer takes 

 this to mark the anterior termination of the frontals, united 

 into one bone. In front of this depression the surface is 

 rough, as if from erosion. On each side of this rough area 



Fig. 13. Proiosphyrcena ziphioides (Cope). No. 2131. 

 , 2- Type of Erisichthe zipkioides Co'pe, seen from below. 

 eth., ethmoid ; /rtr., parasphenoid ; vom.t.^ position of vom- 

 erine teeth. 



Fig. 14. Same rostrum as Fig. 13, viewed from above, with 

 three cross-sections and a longitudinal section of tip. eth.y 

 ethmoid ; yV., frontal; ««., nasals. 



