Cope.] 92 [April 7, 
In the inferior m. 1, the triangles which do not open on one side to the 
anterior loop are 14, then one on each side, and the short wide terminal loop 
whichis bilobed or emarginate in the middle of the end. The ridges, which 
are very prominent and acute, are, therefore, $; at the extremity there are | 
two short ones, between which a third and more prominent one rises a little 
below the grinding surface. A little more attrition would give the distal | 
loop a trilobate outline, and a little more, an acuminate one, from the | 
loss of the lateral angles ; finally the median ridge disappears also. In 
its present state one of the terminal lobes is almost external, making the 
ridges &. 
Measurements. M. 
Length grinding surface............ ere eis eee eee 0.005 
Width eg re os Fe ae are ree aeen cee 0024 
Length fang and crown.............. PN gh ind pal eet ghee: .0078 
The accompanying cut of twice natural size explains the above remarks. 
Two opposite molars held in natural relation by the matrix, resemble 
the above in structure and size so closely as to leave little doubt that they 
belong to the same species. Whether they should be referred to the 
superior or inferior series is uncertain, though analogy with the Hypu- \ 
deus gappert would suggest the latter. They represent the right and 
left second molars, and the triangular areas if isolated, would be 1?, not 
one of them, however, is isolated, the dentine being continuous round the 
entering angles of enamel. The failure of these angles to reach the 
enamel margin of the side towards which they are directed, and an ap- 
proach to parallelism of the entering and projecting enamel plates pro- 
duces a triturating surface, having the form of a succession of Ws. 
This is the reverse of what occurs in Hypudeus gappert according to 
Prof. Baird, where the triangles become confluent at their bases, thus 
extending all across the crown; the same thing is seen in the posterior 
inferior molar in all the species. There is no trace of roots to these teeth 
or that previously described. Length of crown of second molar, m. 0056. 
A third specimen is represented by the molars of both maxillary bones, 
much broken, the posterior of one of the series only being entire. This \ 
tooth is slightly curved, and exhibits three ridges on one side, and four 
on the other; triangles 1? and a short loop with two basal angles, the 
inner more prominent than the other. None of these triangles are isolated, 
put are rather angular expansions of the continuous dentine. The two 
inner angles are much more prominent than the outer, but in old age they 
would probably be equal, judging from their appearance at the base of the 
tooth. Viewed from below, they appear to be closed, showing that the 
character of the group Anaptogonia in this respect is derived from a 
“vetardation”’ of growth in a point which is early attained in true Arvicola. 
M. 
engtn Of CO0tH issih ia Pie ay ais a eae « 0.005 
CHOW Cha Cfagas iat ey raga fe tetiet bella Ces 0.003 
IW LQUULVAPMULAIUGn Mase cr oer coin aaron TaaPCy fois asi ati eae Eee AEN 
