RODENTS FROM THE SIWALIKS. 
3—107 
jaw is somewliat less ; but as the three specimens are otherwise very similar, it 
seems best to regard them as belonging to the same species. In the British 
]\Iuseum there are two rami of the mandible of a fossil rodent from the typical 
Siwaliks, of slightly larger size than the largest Punjab specimen, but evidently 
belonging to the same genus. The general characters of those specimens are very 
similar to those of the Punjab specimens, and, although it is possible that their 
superior size may indicate specific distinction, they may be provisionally associated. 
The following table exhibits the dimensions of the molar series of three of the 
above-mentioned specimens, viz. : 
Ind. Mus. 
Brit Mus. 

N 
Length of three molars 
0-62 
0-67 (?) 
0.74 
Width of m. 2 . 
017 
0-2 
0-25 
Vertical diameter of incisor . 
0 16 
0-16 
0 17 
The number and structure of ^the cheek-teeth (fig. 1), which have a deep enamel- 
fold on the outer, and three minor folds on the inner side, two of Avhich (fig. 2) persist 
as isolated fossetteson the crown of well-worn teeth, show that the specimens belong 
to the sub-family Spalacince of the Spalacidce. This sub-family contains the three 
genera^ Spalax, Heterocephalus^ and Uliizomys. The lower molars of the first are 
distinguished ])y the enamel-folds l^eing very shallow, and disappearing at an early 
stage of wear ; while those of the second have only a single inner and outer fold. 
In Rhizomijs the structure of the molars is precisely similar to that of the Siwalik 
specimens, and the latter may therefore be referred to that genus. 
Calcaneum. — In woodcut fig. 3 there is given an enlarged view 
of the left calcaneum, partially broken on the inner side, of a small 
mammal collected by Mr. Theobald in the Siwaliks of Asnot, which 
may not improbably belong to the jDresent form. The bone is very 
similar to, but somewhat smaller than the calcaneum of R. hadius. 
Distinctness and Affinities. — Taking the s]3ecimen represented in 
fig. 1 as the type, the Siwalik form is distinguished from R. suma- 
TihzomxjK ^‘’cnsis by the smaller size of the jaw and the incisor, although the 
(?) sp. 1-eft caica- length of the molar series is very nearly the same in the two ; the 
Shvaiiksomierun^ individual teeth being wider in the living form. The fossil is nearer 
jab Indian Museum in size to R. pruinos US, but its molars are more elongated, the incisors 
(No. D 9S) f much smaller, and the jaw more slender. It is considerably larger than 
R. hadius, and still more so than R. minor ; but the incisors are only a little larger than 
those of the former, although the molars are half as large again. R. sinensis and R. 
erythrogenjjs are both considerably smaller than the fossil. The writer has not had the 
opportunity of comparing the latter with the African form ; but it is in all proba- 
1 In the preliminary notice alreadjr quoted it has been conclusively shown that the specimens cannot belong to any other 
family. The memoir by E. R. Alston on the “ (Jlassification of the Order Glires ” (‘ Proc. Zool Soc 1876, p. 61), exhibits 
the dental character of the different groups in a very clear manner. 
2 Mi/ospn/ax, Blyth (not Brandt, which= 9?/) /(;/<«.■.), has been shown by Mr. W. T. Blanford Jown. As. Soc. Beug.,’ 
vol. L, pt. 2, p. 118) to be probably identical with lllobiiis, and does not, therefore, belong to the Spalacidm. 
