408 JOURNAL, BOMBAY Is ATURAL HIST. SOCIETY, Vol. XXIV. 



the basal half, both scales and hah's, then quite gradually lightening 

 to white at the tip, the terminal hairs quite white ; below the 

 scales are rather lighter proximally, quite Avhite terminally, and the 

 hairs are white throughoiit ; but the limits of change are nowhere 

 sharply defined. 



Skull on the M'hole fairly like that of J?, vodferans, the] brain 

 ca&e rather broader between the parietal ridges ; zygomatic plate 

 rather more projected forward ; palatal foramina a little longer ; 

 luolar series rather shorter. Incisors similarly forming a large 

 segment of a small circle, their tips more directed backward 

 towards the throat than in J?, hoirersi, and in fact more than in any 

 other rodent that I have examined.* 



* The angle at which the incisors are set in the jaw being a character of con- 

 siderable systematic importance it might be of use if a method could be found 

 of gauging it accurately, instead of merely stating that they are " thrown for- 

 wards" or " turned backwards." I find that if one limb of a small goniometer be 

 placed in the line of the grinding surface of the molars, the angle at which the 

 exposed part of the incisors come down may be fairly accurately measured if the 

 line of the terminal millimeter of their front enamel-clad siirface be put close to 

 and parallel with the edge of the other limb. By this method the incisors of 

 JEpionys listeri may be said to be set at an angle of about 26° or 28° to the line 

 of the tooth row, other members of the same group 28" to 30°, E. raUus about 

 40'3 — 45"^, E. lerdmorei about 45'^ — 50'^. A Bliizomys comes out at 55°, a Bathy- 

 ergus and a Nyctocleptes at 75°, and a Cannomys at about 90°, while thrown out 

 beyond the right angle such an extreme form as Ileliophobius may be measured 

 as'llO'^ to 120^. 



These angles cannot be measured within a limit of accuracy of some 5'^, more 

 or less, but even so they represent an improvement in the direction of defining 

 the set of the teeth, as compared with any attempt to describe it in words. 



Care must be taken that the incisors to be measured are of normal extension, 

 neither accidentally shortened or pushed in on the one hand, nor pulled out or 

 overgrown on the other, as any of these conditions woiild invalidate the results 

 obtained. 



