1903.] Hay, North American Cretaceous Fishes. 2 1 



to have inclined forward. The cutting teeth of the middle 

 of the dentary are only slightly inclined forward, not greatly 

 different from the corresponding ones of the skull described 

 by Felix. The maxilla of the latter is quite different from 

 that of P . dimidiata and that of P. nitida, as represented by 

 the specimens described under that species. In the type of 

 P. dimidiata the maxilla has a length of 137 mm., a width 

 where widest of 17 mm. and where broadest, near the hinder 

 extremity, of 30 mm. The maxilla of Felix's specimen is 

 probably little, if any, longer. The figure gives evidence 

 that little of that of the left side is missing. Its width, where 

 narrowest, is 20 mm.; where widest, at least 32 mm. Of 

 the right maxilla of Felix's specimen perhaps nothing is want- 

 ing and it measures only 130 mm. This indicates that the 

 bone was of considerably heavier construction than in P. 

 dimidiata. If it be contended that the maxilla of Felix's in- 

 dividual belongs to a larger animal and was both longer and 

 broader, it may be shown that it must have contained a con- 

 siderably larger number of teeth. On measuring backward 

 from a point 25 mm. behind the anterior end of the maxilla 

 of P. dimidiata, there are found 9 teeth or alveoli for them, in 

 32 mm. In the same distance on the left maxilla of Felix's 

 specimen are 9 or 10 teeth, or spaces for them. This indi- 

 cates either that the maxilla was no longer or that the teeth 

 were relatively smaller. Indeed, in the portion of the left 

 maxilla represented by Felix, 103 nim. long, there is room 

 for as many of its teeth as are found in the 122 mm. of tooth 

 line of P. dimidiata. Furthermore, the rostrum of the speci- 

 men described by Felix is very different from that described 

 by Cope, as Felix himself has pointed out. 



Protosphyrcena sequax differs from the specimens which are 

 here referred to P. nitida in most of the respects in which it 

 differs from P. dimidiata, viz., in having teeth perpendicular, 

 or nearly so, to the supporting bones and in having a broad 

 heavy maxilla. 



It is, of course, impossible to say that the skull here de- 

 scribed does not belong to some species which has already 

 received a name based on a fin blade. It may, for example. 



