56 MOSASAURUS. 



Jersey, belonging to the museum of the Academy of Natural Sciences. It is 

 represented in Fig. 3, Plate X, and Avas previously indicated and figured by Harlan^ 

 and IVIorton." In form it resembles the corresponding portion of the teeth above 

 described, but is slightly larger. Its dividing ridges are distinctly denticulated; the 

 outer surface is divided towards the base of the crown into four planes, which 

 diminish and finally disappear towards the apex ; the inner surface is divided into 

 eleven planes, Avhich also diminish and become obsolete towards the apex. The 

 length of the crown when perfect has been about two inches and three-quarters ; 

 the antero-posterior diameter at base about thirteen lines ; and 

 the transverse diameter is fourteen lines and a half. 



The base of the specimen is excavated in a trumpet-like 

 manner, extending to a thin edge at the periphery of the 

 crown. This condition evidently indicates the specimen to 

 have been shed during the life of the animal, notwithstanding 

 the little wearing to which the tooth appears to have been 

 subjected. 



The accompanying outlines, No. 3, represent sections from the base, middle, and 

 near the apex of the specimen. 



6. The shed crown of a tooth, from Burlington County, New Jersey, presented 

 to the Academy of Natural Sciences by Mr. L. T. Germain. The specimen, repre- 

 sented in Fig. 6, Plate X, has the apex and base broken, but when perfect appears 

 to have been less than two inches and a half long, about thirteen lines in diameter 

 antero-posteriorly and twelve lines transversely. The ridges of the crown are 

 distinctly denticulated, but separate the surfaces less unequally than in the preceding 

 specimens. The outer surface is subdivided into nine planes, passing into seven 



and then becoming obsolete towards the apex of the crown. The 

 inner surface is subdivided into about twenty planes, diminishing 

 and finally disappearing towards the apex of the tooth. The sub- 

 divisional planes are more or less obscured by longitudinal striation 

 of the enamel, more especially on the inner side. This striation 

 diminishes and finally disappears towards the apex. It does not 

 exist in the specimens previously described. 

 The accompanying outline. No. 4, represents a transverse section of the crown 

 below its middle. 



The base of the specimen is excavated towards the central pulp cavity in a salver- 

 form manner from a broken edge at the periphery about a line and a half thick. 



7. An entire tooth, from Monmouth County, New Jersey, loaned to me for exami- 

 nation, from the collection of Rutger's College, by Prof. Cook. The specimen 

 represented in Fig. 3, Plate IX, I suspect to belong to the forepart of the lower 

 jaw of Mosasaurus. It is smaller, but has the same general form as the entire teeth 

 previously described. 



The crown is more curved than in any of the preceding specimens, but like them 



' Journ. Acad. Nat. Sci., Vol. IV, Tlate XIV, Figs. 2, 3, 4 ; Med. and Physical Researches. 

 ' Synopsis of Organic Remains, &c., Plate XI, Fig. 9. 



