MOSASAURUS. 65 



an orifice with the excavation for the successional tooth. The latter excavation 

 nearly involves the whole of the intra-alveolar portion of the fang. The contained 

 tooth (Fig. 6, d. Fig. 7) is a fully developed crown, with a large interior pulp cavity, 

 extending to the thin edge of the developing fang as usual in dentition. It 

 resembles that of the last described specimen, but is shorter and more robust in its 

 proportions. Further, the acute ridges divide the crown unequally, the outer 

 surface being more extensive and convex than the inner. The surfaces also are 

 strongly wrinkled longitudinally, especially towards the base, and there exists an 

 evident disposition to subdivide into planes, especially on the outer 

 surface, as represented in Fig. 7. The crovra is thirteen lines and a 

 half long, elliptical in transverse section, as represented in the accom- 

 panying outline, No. 23. The antero-posterior diameter of the slightly 

 contracted base is nine lines ; the transverse diameter eight lines. The 

 inner curvature of the base is nine lines and a half, the outer curvature fifteen lines 

 and a half. 



The tooth (Fig. 6, a) occupying a functional position behind the preceding has 

 the crown considerably worn at the apex, and the enamel is also partly worn away 

 at the base antero-externally, and on several positions of the dividing ridges. It 

 resembles the unworn cro\vn occupying the cavity in advance, but the appearance 

 of a tendency in the surfaces to subdivide into planes is less obvious, and, indeed, 

 is hardly evident on the external surface, where it is most so in the other tooth. 



The fang is intimately coossified with its alveolus, and a deep excavation (h) 

 exists at its posterior part internally for a successional tooth. The exserted portion 

 of the fang is eight lines long, and at the alveolar margin occupies a breadth antero- 

 posteriorly of sixteen lines, transversely thirteen lines. 



22. Fragments of both sides of the lower jaw, and of both pterygoid bones, with 

 teeth, from the same individual. The specimens Avere obtained from the Green- 

 sand of Holmdel, Monmouth County, New Jersey, and have been submitted to my 

 examination by Prof. Reiley, of Rutger's College, through Prof. Cook. The teeth 

 preserved in the fragments resemble those above described which have the laterally 

 compressed, smooth crown, and correspond with those which have been viewed as 

 characteristic of the genus Leiodon. 



A fragment of the back part of the right dental bone, represented in Fig. 3, 

 Plate XI, contains a perfect tooth, apparently the penultimate, a portion of tho 

 alveolus behind, and por'tions of the two alveolj in advance. 



The outer surface of the bone is a vertical plane, rounded at the alveolar border 

 and broken at the lower. The back end is broken off, and the oblique border below 

 is that for articulating with the coronoid bone behind. A large vasculo-neural 

 foramen, opening into the dental canal along the middle of the specimen, is situated 

 below the tooth retained in the specimen. Part of a similar and smaller foramen 

 is also situated rather higher at the anterior broken border. 



The tooth preserved in the fragment has its fang coossified with 

 the alveolus and the border of the jaw. It bears a near resemblance 

 with the specimen described under No. 20. The crown, situated 

 somewhat obliquely with its outer face directed forward, is an inch 



9 April, 1865. 



