MOSASAURUS. 



59 



' 13. A tooth, which has lost its fang, from Monmouth County, New Jersey, pre- 

 sented to the Academy of Natural Sciences by Charles C. Abbott. It is represented 

 in Fig. 11, Plate X, and measures two inches in length. Its apex is worn, and it 

 is invested with enamel to the extreme base of the specimen. It 

 bears a near resemblance to the crown of the preceding speci- 

 men, but is much larger. The base is circular in section, and 

 measures an inch in diameter. The inner surface is slightly more 

 extensive than the outer one, as seen in the accompanying sections. 

 No. 11, taken from the base and above the middle of the crown. 

 Both surfaces are devoid of the faintest trace of subdivision into 

 planes, and are separated by the usual minutely denticulated ridges. 

 The centre of the broken base of the crown exhibits the funnel-shaped summit of 

 the pulp cavity, the wall of which at the broken border of the specimen is four 

 lines thick. 



14. Nine teeth, coossiiied with small attached portions of the jaw, from Mon- 

 mouth County, New Jersey, presented to the Academy of Natural Sciences by Dr. 

 J. H. Slack. They were found together in the same marl pit, and have every 

 appearance of having belonged to the same individual. 



One of the specimens, represented in Figs. 8, 9, Plate X, is about five inches and 

 a half in length. The apex of the crown is worn off more than in any other speci- 

 men of the kind I have ever seen. The dividing ridges are also considerably worn, 

 though enough of one remains to ascertain that they were 

 minutely denticulated. In its present condition the crown is two No. 12. 



inches long, and its nearly circular base measures fourteen lines 

 and a half antero-posteriorly and fourteen transversely. The 

 inner side is more extensive than the outer ; the former being 

 twenty-six lines in circumference at its base, the latter twenty 

 lines. The inner surface is distinctly subdivided into nine planes ; 

 the outer into seven. The accompanying outline. No. 12, repre- 

 sents a transverse section near the base of the crown. 



The extra-alveolar or exserted portion of the fang continues the cone of the 

 crown, and is fourteen lines long by about two inches in diameter at the base. The 

 intra-alveolar portion of the fang is two inches and three-quarters long, and appears 

 to be a constituent portion of the jaw, so intimately is it coossified and continuous 

 with its alveolus. Its inner- side posteriorly is deeply excavated, as represented in 

 Fig. 8, c, for the accommodation of a successional tooth. 



A second specimen, represented in Fig. 7, Plate X, closely 

 resembles the former, except that the inner and outer surfaces 

 of the crown are nearly equal in extent, and are each divided 

 into six principal planes, of which one presents a partial but 

 feeble subdivision. The crown, very much worn at the apex 

 and along the anterior ridge, in its present condition is two 

 inches in length, and thirteen lines in transverse diameter at 

 base, while the antero-posterior diameter has been about fourteen lines. The inner 

 circumference of the base is about twenty-three lines, the outer twenty-two lines. 



