846 MR. O. THOMAS ON THE [Nov. 17, 



naked, are seen on closer inspection to be furnished all oyer with fine 

 scattered hairs, which give no general appearance of a hairy covering, 

 being so fine and so nearly the colour of the skin as to be almost 

 invisible. 



The tail is rather more than half the length of the body without 

 the head, tapers rapidly from its broad and flattened base to its tip, 

 and is thinly covered with fine bristly hairs similar in character to 

 those on the muzzle. 



The feet of Heterocephalus (Plate LIV. fig. 3) are by far its most 

 highly specialized parts, as might, indeed, be expected in so purely 

 burrowing an animal. The anterior pair are large and strong, and 

 the toes are much longer in proportion to the palm than is the case 

 in Georychus. On the proximal half of the palm there are two 

 unusually large and well-developed pads, the rest of the palm being 

 quite smooth ; in Georychus the pads are quite rudimentary. The 

 poUex, though short, is fully developed and is provided with a 

 minute pointed claw ; the fingers are broad and flattened and are 

 provided with similar small conical claws. The third toe is the 

 longest, the second and fourth are about equal, and the fifth, without 

 its claw, reaches to about the middle of the first phalanx of the 

 fourth, and the poUex to the level of the base of the second. 



The hind feet, like the fore, have rather long toes in proportion to 

 their length of sole, and in the same way the tbot-pads on the sole are 

 restricteci to its posterior half, there being only three pads, two near 

 the heel and the third at the base of the fifth toe (Plate LIV. fig. 3). 

 The toes have much the same proportions as those on the fore feet, 

 except that the hallux is relatively longer than the pollex, and the 

 second toe is slightly longer than the fourth. 



The most noticeable character of the feet, however, and one quite 

 unique among burrowing Rodents, is the presence of fringes of fine 

 bristles round their edges. These bristles are not unlike those on 

 the hind feet of the Water-Shrew {Crossopus fodiens), except that 

 they are longer, further apart, and far finer. They grow all round 

 the edge of each toe, and pass backwards along the sides of the feet 

 to the wrists and ankles, although there is a gaj) in the series where 

 one would suppose that they would be most wanted, viz. along the 

 outer side of the fifth hind toe, where they are quite absent and have 

 perhaps been worn oif. The value of these cilia, by which the 

 spread of the foot is largely increased without any increase in 

 cumbrousuess, to an animal which passes its life burrowing in a light 

 sandy soil, is sufficiently obvious to need no comment. 



I am unfortunately unable to make out the number of the mammae, 

 as, owing no doubt to our specimen having been captured out of the 

 breeding-season, they are so small as to be only in one or two 

 instances distinguishable from the minute warts with which the 

 animal's uaked skin is covered. 



The small intestine measures about 115 mm., the short rounded 

 caecum about 12 mm., and the combined colon and rectum about 67 

 mm., 58 per cent, of the small intestines. 



The palate-ridges (Plate LIV. fig. 2) consist apparently of about 



