MOSASAURUS. 61 
The contiguous sides of the two fangs are likewise excavated together for the 
accommodation of a successional tooth, as seen at the middle of Fig. 5, e, and thus 
the two teeth exhibit cavities for the accommodation of three successors, 
The sixth specimen is represented in Fig. 6, Plate LX, and consists of a tooth of 
nearly the same size and form as that in the specimen last described. 
The crown when perfect has measured over two inches in length; and at base it 
measures fourteen lines in diameter antero-posteriorly, and twelve lines and a half 
transversely. ‘The inner surface is rather more extensive than the outer, and is 
divided into seven planes, while the latter presents six planes. ‘The curve of the 
base of the inner surface measures two inches, that of the outer surface twenty 
lines. The lower of the accompanying outlines, No. 16, repre- 
sents a section near the base. The fang upon its inner part is 
almost one-half excavated to accommodate a successor, as 
represented in Fig. 6, e. The excavation has exposed the 
lower half of the pulp cavity, seen at f. 
The seventh specimen consists of an entire tooth, repre- 
sented in Fig. 10, Plate X, nearly resembling the two last 
described teeth. 
The crown is two inches in length, elliptical in transverse section, and measures 
at base antero-posteriorly fourteen lines and a half; transversely twelve lines. ‘The 
inner and outer surfaces are nearly equal, and are rather less distinctly subdivided 
into planes than in the preceding specimens which accompanied this one. The 
upper of the accompanying outlines, No. 16, represents a section near the base of 
No. 16. 
the crown. 
The fang anteriorly and postero-internally presents two excavations for the accom- « 
modation of successional teeth, as represented in Fig. 10,c,d. The postero-internal 
excavation communicates with the pulp cavity, as seen at e. 
The eighth specimen, represented in Fig. 4, Plate X, has the general form and 
proportions of its companions, but is smaller, except the fourth specimen above 
indicated, which it most nearly resembles. 
The crown is twenty-two lines long, elliptical in transverse section, and measures 
fourteen lines in diameter at the base antero-posteriorly, and eleven lines and a half 
transversely. Its most remarkable peculiarity consists in the possession of a single 
carina or ridge situated posteriorly along the concave border; the ridge being 
minutely denticulated as in those of preceding specimens. ‘The anterior border of 
the crown is thick and convex, and towards the apex presents several prominent 
vertical folds. The inner and outer surfaces, of equal extent, are 
feebly subdivided into traces of from four to six planes. ‘The 
upper pair of accompanying outlines, No. 17, represent transverse 
sections near the base and apex of the crown. The fang is deeply 
excavated postero-internally, as seen in Fig. 4, d, for the accommo- 
dation of a successor, but the excavation has not exposed the 
pulp cavity of the tooth. 
The ninth, or remaining specimen of the series under exami- 
nation, is represented in Fig. 5, Plate XI, and. is a miniature resemblance of the 
No. 17. 
