Stewart.] Cretaceous Fishes, 369 



at the base, but enough remains to show that this and the an- 

 terior one were the smallest of the four. The two in the center 

 are of about the same size ; they are all directed forward, the 

 anterior slightly more so than the rest. These teeth all have 

 broad lanciform crowns, with anterior and posterior cutting 

 edges and slightly striate enameled surfaces. Just back of the 

 most posterior of these large teeth there is a row of small teeth, 

 the anterior of which are scarcely more than bony tubercles, 

 but posteriorly they assume definite dental characters ; ten of 

 these are preserved in the specimen. There are other teeth like 

 these on the anterior portion of the border, but owing to the tip 

 being broken away, the exact number of these cannot be deter- 

 mined. The surface for the maxillary contracts toward the an- 

 terior end, and is bounded below by a narrow shelf of bone 

 extending inward. 



Approximate length of the alveolar border 82 mm. 



Depth just back of last large tooth 27 " 



Height of first large tooth 15 " 



Height of second large tooth 19 " 



Protosphyrasna penetrans. Plate LXIII. 



Proto8phyrcena penetrans Cope, Bull. U. S. Geol. Surv. Terr. 1877, vol. 

 in, No. 1, p. 821. 



This species is represented in the museum by only one speci- 

 men, Xo. 372, consisting of a rostrum with a small portion of 

 the apex, and the basal portion with the large teeth absent. 



Rostrum of Protosphyrcena penetrans y one-half natural size. 



The superior distal surface was probably rounded in life, but, 

 owing to depression, it has become slightly flattened, giving the 

 cross-section at this point a somewhat ovoid or elliptical outline. 

 In P. nitida this surface is finely rugose, with a strong angle 

 bounding the superior plane on each side, while in this species 

 there is no such angle, and the markings on this surface vary 



