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, 7, 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 crown 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 crown 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 (>) 
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 were 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 the 
alveolus behind, and portions 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 hone 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, 1866. 
No. 23. 
No. 24. 
