SXWALIK AND NARBADA EQUIDiE. 
19—85 
I cannot identify the molars of the present species with any of the American 
species of the genus, which are mostly characterised by their smaller size, and by 
the lesser degree of plication of the central enamel islands. 
Mandible. — In figure 2 of plate XII there is figured a portion of the left 
ramus of the mandible of a Rippotherium , obtained by Mr. Theobald in association 
with the maxilla last described, and which doubtless belonged to the same individual. 
The specimen was, in all probability, originally complete, but has been broken, and 
lost some pieces during the process of extraction from its bed. The parts now 
remaining comprise the greater part of the left ramus, from the base of the coronoid 
process to the commencement of the symphysis, but wanting a small part of the 
middle, and the last premolar. The other fragment consists of the hinder half of 
the right ramus as far as the front of the last premolar. The figured fragment 
shows the second and third premolars (pm. 2, pm. 3), and the three true molars (m. 1 
to m. 3), while the right ramus contains the last premolar and the true molars. 
The jaw belonged to an animal which had just attained to full maturity, as the 
last true molar has been but a short time in use. The first premolar, or milk-molar, 
has disappeared. The teeth are of large size and great thickness, and the premolars 
are much larger than the true molars. 1 The cement is of unusual thickness, 
forming distinct ledges on the sides of the crown. The free edges of the enamel 
are slightly crenulated. The inferior border of the ramus is nearly straight below 
the molars, and the inflection for the symphysis commences one inch in advance of 
the second premolar. The dimensions of the specimen (combining those of the 
two rami) are as follows : — 
Length of six molars ......... 6'8 
Depth „ jaw at second premolar ....... 2‘08 
„ „ „ „ last true molar . . . . . . . 41 
Length „ second premolar . . . . . . . .1*3 
Width „ „ 072 
Length „ third „ ........ i - 13 
Width „ „ ........ 0-8 
Length „ fourth „ ........ ri2 
Width „ „ 075 
Length „ first true molar . . . . . . . . l'O 
Width . . . . . . . 0'68 
Length „ second T07 
Width . 062 
Length „ third 1‘3 
Width „ „ . . ... . . '. . 061 
Distinctions and differences. — The above dimensions indicate an animal of 
somewhat larger size than the Tibetan kiang ( Equus hemionus). The teeth are 
larger and stouter than those we have assigned to R. antilopinum, the increase of 
thickness being due in great part to the large quantity of cement. The inferior 
border of the jaw seems to be straighten than in that of H. antilopinum. Much 
In the figure the space left for the last premolar is not of sufficient length. 
