MOSASAURUS. 



63 



described. It also bears a near resemblance to a specimen described by Prof. E. 

 Emmons,^ under the name of Elliptonodon compressus. 



The enamelled crown is an inch and a half long, and is elliptical in transverse 

 section, as represented in the accompanying outlines, No. 19, representing sections 

 below the middle and at the base. The latter measures an inch 

 antero-posteriorly, and ten lines transversely. The acute ridges 

 divide the crown into two surfaces about equal in extent and con- 

 vexity. The surfaces exhibit a faint disposition to subdivide 

 towards the base, but for four-fifths of their length are smooth. 

 The transverse annulation, represented by the artist in the figure, 

 is only one of staining of the enamel, though there is a feeble 

 constriction of the crown corresponding with the band above its middle. The base 

 of the specimen is excavated in a funnel-shaped manner from a thin sharp edge at 

 the periphery to the central pulp cavity. 



18. Two specimens of teeth, from Mount Holly, Burlington County, New Jersey, 

 contained in the museum of the Academy of Natural Sciences. 



One of the specimens, represented in Fig. 9, Plate IX, consists of the shed crown 

 of a tooth, much worn at the apex. In its present condition it measures nineteen 

 lines long, extending from the enamel border at the base, and in transverse section 

 is elliptical, as represented in the outer of the accompanying outlines, No. 20. The 

 antero-posterior diameter at base, in the perfect condition, measured sixteen lines, 

 and the transverse diameter is thirteen lines and a half. The surfaces, about 

 equally divided by the anterior and posterior acute ridges, are entirely devoid of 

 subdivisional planes. The enamel is more rugose than in any of the preceding 

 teeth, but otherwise I can see no important difference between it and several of 

 those last described. The base is excavated in a salver-form manner, from a broken 

 edge about a line in thickness, to the central pulp cavity. 



The second specimen, represented in Fig. 10, Plate IX, 

 consists of a comparatively small tooth, with the apex of the 

 crown broken off so as to expose the summit of the pulp cavity. 

 In color and general character the specimen looks as if it may 

 have belonged to another part of the dental series of the same 

 individual as its larger companion. 



In form the crown has nearly resembled that of the specimen described as No. 

 12, represented in Fig. 4, Plate IX. When perfect it has measured about thirteen 

 lines long ; and its circular base is eight lines in diameter. It is irregidarly divided 

 by the acute ridges, of which the anterior is almost entirely obliterated by wear. 

 The inner surface is much more extensive than the outer, and both are smooth, 

 presenting neither trace of subdivisional planes nor rugosities. The inner curve of 

 the base is fifteen lines and a half, the outer curve eleven lines. The inner of the 

 accompanying outlines, No. 20, is a transverse section from the base of the crown. 



. The straight fusiform fang is two inches and a quarter long, and appears as if it 

 had not been coossified with its alveolus. Just back of the centre of the inner side 



North Carolina Geological Survej^, 222, figs. 41, 42. 



