AND AVES OF NORTH AMERICA. 



199 



The fang-like supports of all the teeth are more firmly ooossifted with the jaws, than is usually the case in this 

 family, anil most of them contain excavations for the successional teeth. On the outer superior edge of the lower 

 jaws there is a, row of pits round or oval in outline, and alternating with the teeth. In most instances one is situated 

 outside and a, little in front of each tooth, and those? in the anterior portions of the jaws are deeper than those farther 

 baok. They evidently have been excavated for the maxillary teeth, and are adapted for their reception, like the sim- 

 ilar cavities in the jaws of crocodiles. Slight depressions, corresponding to these in position, may be seen in the jaws 

 of some of the larger species of Moaasaurus, and the unusual depth of the pits in the present specimen is probably due 

 to the more pointed character of the teeth. 



A mono the pieces of the skull preserved, is part of a, symmetrical hone, about seven inches in length, which 

 formed the superior, medial portion of the face in front of the orbits. Although no sutures are visible, it is evidently 

 composed of the na.sal bones, and portions of the attached premaxillary and frontal bones. Its upper surface is very 

 peculiar in form, and is doubtless quite characteristic of the species. It, is slightly oonoave in front where broken off, 

 flat at Its narrowest part between the nasal openings, convex as it becomes broader a little farther back, next flat with 

 regular beveled edges at its greatest width between the apertures, and finally very convex as it again expands before 

 coalescing with the medial frontal. This fragment indicates that the nasal bom? was very slender, and like the pre- 

 maxillary undivided, that the superior nasal openings on either side were long and narrow, and that the central line 

 of the face immediately behind them was marked by a low rounded ridge. 



From the Lower bed of Cretaceous Green Sand at Marlborough, Monmouth Co., N. J. 

 The size and horizon of this species arc quite similar to those of the Clidastes iguanavus. 



MOSAS ATI KITS MIERSII, Marsh. 



Sill. Amer. Jour. Sci. Arts, 1869, 395. 



The following description is derived from Marsh, 1. c. 



This species is indicated by the crown of a single tooth which was found in the lowest marl bed, near Horners- 

 fcown, New Jersey. It evidently belonged to a, Mosasauroid reptile of moderate size, but, appears to differ from tin? 

 teoth of any yet described, in being more pointed, arid in having the sides very deeply facetted or grooved. It rcscm 

 bles strongly the teeth of Mosasaurus adpeanus, but is more compressed, Hie enamel of the crown more corrugated, 

 the cutting edges are minutely denticulated, and it, evidently belonged to a, much larger animal. The crown is an inch 

 and live lines in Length, and eight lines in antero-poslerior diameter at the base. The facets fade away before reach- 

 ing the apex, which is nearly smooth. 



This tooth is apparently too large for either of the species of Baptoaaurus described below, the remains of which 

 were found in the same Immediate vicinity, but, it, may possibly belong to Liodon lavis, the teeth of which are 

 unknown. 



PLATECARPUS, Cope. 



I'roc. Host. Soc. Nat. Hist,., IK(i!). 264. 



This genus is especially characterized by the peculiar insertion of the pterygoid teeth. 

 Its humerus also is more chelonian than that of Mosasaurus, while the os quadratum pre- 

 sents marked differences. These peculiarities have been pointed out by Leidy, who refers 

 the species to the genus Holcodus of Gibbes. Now this genus, Leidy also shows, was 

 made to include, also, teeth of Hyposaurus, but the name, as its meaning is "grooved 

 tooth," should he restricted to that Mosasauroid genus, to which it is applicable. 



