Vol. 5] 



Merriam. — A Prim itive Ich th yosa uria n . 



385 



anterior teeth have approximately the same height as the pos- 

 terior one, but have the form of simple cones, rather than of 

 laterally compressed domes. In the teeth of both jaws the 

 crowns are swollen just beyond the base, but this feature is par- 



Fig-. 2. — Phdlarodon fraasi. Skull ami dentition. No. 9853, natural 

 size. D, dentary; Sa, surangular; M, maxillary; L, lachrymal; Pf, pre- 

 frontal; F, frontal; N, nasal; n.o,, narial orjening; p.g., groove for reception 

 of posterior end of premaxillary. 



ticularly noticeable in the anterior teeth of the upper jaw, in 

 which the bases of the crowns are much larger than the roots. 

 The enamel of several of the larger teeth shows a tendency to 

 develop radial wrinkles. On the anterior pair of teeth in the 

 upper jaw the enamel is practically smooth. As nearly as can 

 be determined, the anterior upper tooth is set in a shallow pit at 

 the bottom of a shallow, longitudinal groove. 



SKULL. 



The general form of that portion of the skull preserved in 

 specimen 9853 is in many respects closely similar to that in the 

 Ichthyosauria. Anterior to the middle region of the orbits the 

 head narrows gradually to the most anterior point on this speci- 

 men (fig. 3). Judging from the form of the skull as shown 

 here, the rostrum was rather slender and pointed, though it may 

 have been shorter than in the typical ichthyosaurs. The skull 



