34 Memoirs of the Indian Museum. [Vol. I, 



bullae are nearly twice as large as in Mus, smooth, round and prominent ; Blanford 

 describes the infraorbital foramen as typical ; the lower portion very narrow, the 

 outer portion slanting forward from the base, then broadly rounded and deeply sinuate. 

 The zygoma tends to be angular in its sweep outwards and downwards, and is heavy 

 and solid. The nasals instead of projecting over the gnathion as in Mus, fall 2 mm. 

 short of it. The occipital bone slopes backwards and downwards, but less markedly 

 than in M. decumanus. 



Variations. — The posterior border of the interparietal is, as a rule, straight, giving 

 the posterior end of the cranium a very square appearance, but in 25 per cent, of skulls 

 it projects backwards in a point running to meet the occipital crest. In two instances, 

 out of 25 skulls examined, the posterior border was actually slightly concave forwards, 

 so that the bone was crescentic with the horns pointing back rather than forwards, 

 vide fig. 54. The coronoid suture is generally curved as shown in fig. 54, but it 

 may be angular, the limbs being 120° apart. This was seen twice. In one skull the 

 curve, instead of being represented by one angle, was broken into two by a backward 

 projection of the frontal, which was truncated. 



The anterior palatine foramen is very narrow, particularly posteriorly, where it 

 becomes slit-like. It is very slightly longer than the upper molar series, being y6 

 mm. against yi mm. 



The nasals show practically no variation except in one instance. No. 127, in 

 which they are only 7-5 mm. against an average of ii-6 mm., or 1875 per cent, 

 against 29-4 per cent, of the total skull length. 



In addition to the measurements of 20 skulls, a table is given comparing the mea- 

 surements of my own series with those of the Indian Museum series and a few skulls 

 of Mus (Nesokia) kok, the slightly smaller, sometimes redder southern variety. The 

 Museum series, from different parts of India, averages larger than mine, though the one 

 specimen collected in Calcutta agrees with my average. The Museum series are old 

 skulls. The smaller N. kok series, on the other hand, are fairly young ; three out of 

 the six show a marked supernumerary cusp or lamina in the second molar, and two 

 show traces, while in only one has it disappeared. 



