MOSASATJRUS. 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 IX, 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 /. 



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 outlmes, No. 16, represents a section near the base of 

 the crown. 



The fang anteriorly and postero-internaUy presents two excavations for the accom- 

 modation of successional teeth, as represented in Fig. 1 0, 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. 1 7, 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 



