284 Mr. M. A. 0. Hinton on 



Description. — In dorsal colour this form makes a nearer 

 approach to dichrurus than to other subspecies of gambianus ; 

 but the cranial characters are closely similar to those of olivice. 



In its harsh loose fur, cold grey dorsal colour, and sharply 

 contrasted dusky ears, C. g. grahami resembles the other 

 races of gambianus. In general external appearance, length 

 and quality of the fur, markings of the hands and feet, and 

 in the relative proportions of the black and white of the tail 

 it agrees best with dichrurus. In the latter the black hairs 

 of the back are so abundantly developed tliat one could 

 almost describe the rump as being tl clouded " with black; 

 in grahami this is not the case, although the black hairs are 

 far more numerous and obvious than in true gambianus and 

 olivia?. The specimens obtained by Emin Pasha in Monbuttu 

 are lighter-coloured and have thinner fur. 



In the skull the nasals are a little shorter relatively than in 



anterior palatal foramina are also short relatively ; their 

 length equals 8*6 °/ of condylo-basal length in grahami, 

 89— 11'6 % in olivice, and 11*7-13 "/ in dichrurus and 

 gambianus. 



As is well known, the cranial differences observable 

 between closely allied species or subspecies of rodents chiefly 

 involve characters which depend upon the greater or less 

 development of one or other of the elements of the jaw- 

 musculature. Iu order to appreciate such differences it 

 seems better to compare the measurements relating to them 

 with a standard representing the working surface of the jaws 

 alone rather than with one which involves the brain-case as 

 well ; the length between the anterior face of the upper 

 incisor and the posterior edge of m. 3 seems to be a good 

 constant for such a purpose. In the subjoined table certain 

 measurements relating to the masseter and temporal muscles 

 are shown as percentages of this constant. With regard to 

 the masseter system, the anterior part of the masseter medialis, 

 passing through the infraorbital canal, would seem to be most 

 strongly developed in gambianus and dichrurus, while its 

 surface of origin is shortened and its bulk slightly reduced in 

 grahami, the reduction in bulk being carried still further in 

 olivice ; the development of the masseter lateralis in so far as 

 it is indicated by the diameter of the zygomatic plate seems 

 to stand, generally speaking, in an inverse relation to the 

 development of masseter medialis. Characters dependent 

 upon the development of the temporal and pterygoid muscles 



