159—18 INDIAN TERTIARY AND POST-TERTIARY YERTEBRATA. 
M. Filliol with E. velaunus, there is a distinct ridge present on each column, but, as 
in the other European forms, the external angles of each of the outer columns, are 
much more developed than in the Indian teeth, and project outwardly beyond the 
plane of the median ridges, in much the same manner as in the molar represented in 
figure 5 of plate XXIII. of the present memoir. The presence of these ridges in 
the Isle of Wight teeth, and them apparent absence in those of the continental E. 
velaunus would seem to throw some doubt on M. Filliol’ s identification of the two 
forms. In the sequel E. vectianiis is still provisionally classed as a distinct species, if 
only for the sake of convenience of reference. In E. americanus 1 (distinguished by 
its taller columns, and larger fifth column), and in the small II. gresslyi , 2 the median 
ridge is more developed than in any other non-Indian form, but still much less so 
than in the Indian teeth. The other European forms are of smaller size, and do not 
approach closely to the Indian teeth. 
On the whole it would seem that there is little, if any doubt, but that the 
Indian teeth should be referred to the genus Eyopotamus, but that they belong to a 
slightly abnormal division of it. This reference will be found to be of considerable 
importance with regard to the generic determination of the teeth of the next species. 
The dimensions of the specimen represented in figure 4 are as follows : — viz ., 
length, (>8 inch ; breadth, 089 inch ; height of crown, 045 inch. The specimen 
represented in figure 6 is of slightly larger dimensions. 
Lower molar . — In figure 3 of plate XXIII, there is represented the greater portion 
of the third left lower molar of a liyopotamid, obtained by Mr. W. T. Blanford in 
Sind. The tooth has lost its third, or last barrel, but is otherwise perfect, and is in an 
intermediate condition of wear.: it agrees in all general respects with the lower 
molars of Eyopotamus , and is of about the same size as the last lower molar of the 
European E. bovinus. The crown is, however, lower than in most European forms, 
in which respect it corresponds with the upper teeth. The size of the tooth renders 
it rather large to have belonged to the same species as the upper molars described 
above, which are nearly equal in size to those of E. vectianus , but since we have 
seen that there is some variation in the size of the upper teeth, and as it is extremely 
undesirable to form new species on such scanty evidence, and without a fair amount 
of certainty, it seems better to provisionally refer the lower tooth to the same species 
as the upper. It may be added that the tooth is readily distinguished from the lower 
molar of Merycopotamus by the greater stoutness and breadth of the barrels, by the 
more rounded contour of the inner columns, and by the smaller degree of elevation 
and sharpness of the whole crown, and especially of its outer columns. 
Mandible. — In figure 4 of plate XXIV. there is represented, from the external 
aspect, the portion of the left ramus of the mandible noticed in the passage in the 
1 Leidy, “Jour. Acad. Nat. Sci. Philad,” Vol. VII., pi. XXI., fig. 1. An excellent woodcut of an upper molar is 
given by Professor Cope “ Origin of Types of Molar Teeth, etc,” Philadelphia, 1874, p. II., fig. 8. The comparisons given 
in the text are chiefly made from a cast of the molars in the British Museum. 
2 Pictet, “ Paleontologie Suisse,” Vol. V., pi. XXIV., figs. 12 and 13. 
