326 



EODENTIA. 



Measurements of JRhizomys 2')ruinosus. 



Muzzle to vent 

 Length of tail 



of fore foot . 



of first toe . 



of middle finger . 



of hind foot 



of first toe 



of middle toe 

 Eye to eye, inner angle (callipersj 



,, to ear (callipers) 

 Ear to ear (callipers) 



The skull of ll.x>ruinosit,s, Blytli (see Plate XVI, figs. 1 — 3), is very distinct from 

 that of R. badms, Hodg., from which it is distinguished by its much greater size and 

 by the flattening and exjjansion of the frontal region behind the nasals and by the 

 backward prolongation of the ridges from the external orbital angle of the frontal 

 which form nearly one-half of the upper and inner margin of the zygomatic fossa, 

 while in B. badius, Hodg., these ridges being directed inwards to the middle line 

 unite immediately behind the nasal bones. In JR. pruinosus, Blyth, the premaxillaries 

 do not extend behind these bones, while in JR. badius, Hodg., they do, and almost 

 embrace their hinder extremities. The frontal contraction also of JR. pruinosus, 

 Blyth, is situated much farther back than in JR. badius, Hodg., so that the posterior 

 division of the brain-case is much more truncated than in the latter species. The 

 zygomatic arch also is more rounded and outwardly projected in the latter. In 

 R. pruinosus, Blyth, the surface of the palate, immediately behind the premaxillary 

 foramina, is broad and rather deeply excavated, the concavity being laterally defined 

 by two well marked ridges, while in R. badius, Hodg., there is no such concavity, 

 the mesial line being occupied by the elevated and rounded margins of the 

 palatine surfaces of the maxillae. The palatine surfaces of the palatines of R. 

 pruinosus, Blyth, are flat, and expanded, and on the same plane with the similar 

 surface of the premaxillaries the mesial line of union of which is not marked by any 

 median ridge, whereas in R. badius, Hodg., the palatine surface of the maxillaries is 

 rather deeply concave from side to side, and the mesial line is occupied by a ridge, 

 the same aspect of the palatines being considerably reduced, much transversely 

 concave, and sloped upwards and backwards, the wings of the sphenoid being con- 

 siderably less divergent than in R. pruinostis, Blyth. These differences at once 

 suffice to separate R. badius, Hodg., and R. minor. Gray, from R. pruinosus, Blyth, 

 and they confer an altogether different conformation on the opening of the j)osterior 

 nares to that which distinguishes R. p>ruinosus, Blyth, in which the palatine margin 

 is broad and transverse, while in these two other species it is narrow and arched. 

 The nearest ally of the skull of R. pruinosus, Blyth, would appear to be the skull of 

 R. sinensis, Gray, which has the flattened palate and the expanded frontal region of 

 this species, but differs from it in its narrower palate, shorter and broader muzzle, 



