MOLAR TEETH AND OTHER REMAINS OE MAMMALIA. 
19 
the posterior valley {in the middle of the right side of the figure) is very deep, and 
almost perfectly oval in form ; the pass leading into this vaUey from the posterior 
side of the tooth is divided by a median fissure. 
The antero-external angle of the tooth {^eft-hand top-corner of the figure) is 
produced into a prominent vertical buttress (as in Bhmoceros jamnicus and R. siva- 
lensis) divided by a median groove, so that the enamel in this part of the crown- 
surface forms two contiguous arches. Owing to the depth of the outer end of the 
anterior valley, the worn-crown would present an isolated fossette at this point, 
or two fossettes in all. 
On the dorsum, the free edge forms a nearly horizontal line ; the surface is 
concave antero-posteriorly. The costae of the buttress do not extend as far as the 
neck of the tooth. The measurements are as follows 
External side ... ... ... ... ... 3-6 
Internal side ... ... ... ... ... 1'9 
Anterior side ... ... ... ... ... 2‘7 
Posterior side ... ... ... ... ... 2'0 
Thickness of enamel on outer side ... ... ... ... O’ 1 
Ditto on sides of median valley ... ... ... 0’06 
Width of base of anterior eollis ... ... ... ... I’O 
Ditto median ditto ... ... ... ... 0’7 
Height of summit of tubercle above neck ... ... ... 0’4 
Height of lowest part of cingulum above neck ... ... ... 0’5 
The ether specimen {plate 5, fig. 2) is from the bone-beds of the Irawadi ; 
it is the second upper molar of the right side. The whole of the grinding surface 
is complete, but a considerable portion of the base of the external wall and the 
anterior angle has been broken away; the crown is much less worn than that 
of the last specimen. 
The tooth being of the same form as the last, it is only necessary to note a few 
points. 
The median eollis {on the left side of the figure) is somewhat twisted upon 
itself, and constricted in the middle : the pass into the posterior valley {the middle 
of the left side of the figure) is more deeply cleft than in the last specimen, the 
outer half being higher than the inner. 
The crochet becomes gradually thinner towards its summit, and is sharply bent 
inwards on itself ; a small process of enamel is seen at the outer extremity of the 
median valley, which may, perhaps, be the rudiment of a combing-plate. The 
measurements of this specimen are as follows : — 
Length of external surface 
Ditto internal surface 
Ditto anterior surface 
Ditto posterior surface 
... 2-6 
... 1-9 
... 2-3 
... 2-0 
( 37 ) 
