MOSASAURUS. 57 
presents its inner and outer surfaces separated by minutely denticulated ridges, and 
subdivided, though less distinctly, into narrow planes. ‘The length of the crown is 
twenty-two lines; its antero-posterior diameter at base eleven lines; its transverse 
diameter twelve lines; its inner circumference twenty-eight lines; and its outer 
circumference eleven lines. ‘The inner surface is obscurely subdi- 
vided into nine or ten planes, disappearing towards the apex of the 
crown ; the outer surface into three or four planes, equally obscure, 
and disappearing in the same manner. The accompanying out- 
lines, No. 5, represent sections at the base and near the apex of * 
the crown. 
The fang is moderately curved, cylindroid, and measures about 
two inches and a half in length, of which the extra-alveolar portion 
comprises about half an inch. ‘The bottom presents an elliptical funnel-shaped pit 
narrowing into the canal of communication with the pulp cavity. The sides of 
the fang exhibit no trace of excavations corresponding with cavities for succes- 
sional teeth. . 
8. A tooth, from Monmouth County, New Jersey, presented to the Academy of 
Natural Sciences by Dr. J. H. Slack. The specimen, represented in Fig. 2, Plate 
IX, resembles that last described so nearly that it looks as if it might have been 
derived from the same individual, though it is considerably smaller. 
The crown is seventeen lines long, with the base eight lines in diameter antero- 
posteriorly and seven lines and a half transversely. ‘The surfaces of 
the crown are less unequally divided than in the preceding specimen 
by the usual ridges, which in this case are rather obscurely denticu- 
lated. The outer surface of the crown is subdivided into four planes, 
merging into three and disappearing towards the apex; the inner 
surface is subdivided into eight planes, likewise becoming obsolete 
towards the apex. The accompanying outlines, No. 6, represent transverse sections 
of the crown from near the base and apex. 
The fang is twenty-three lines long, and closely resembles that of the preceding 
specimen, in its form, the entrance to the pulp cavity, and in the absence of an 
excavation produced by a successional tooth. 
9. A mutilated tooth, which accompanied the latter specimen, from the same 
locality and donor. It is larger and has a proportionately shorter and more robust 
fang than the preceding. The crown is more equally divided by 
the usual ridges, and the surfaces are more distinctly subdivided 
into planes; the outer surface exhibiting five, the inner surface 
nine, ‘These indistinctly multiply near the base of the crown, 
and diminish in number and finally become obsolete towards the 
apex. ‘The antero-posterior diameter of the base of the crown is 
eleven lines; the transverse diameter nine lines. The accompany- 
ing outline, No. 7, represents a transverse section near the base of 
the crown. 
The fang is compressed from without inwardly, and measures two inches in 
length ; sixteen lines antero-posteriorly, and twelve lines transversely. It presents 
8 April, 1865. 
No. 5. 
No. 6. 
No. 7. 
No. 8. 
