EAST AFEICAN MAMMALS IN NATIONAL, MUSEUM. 159 



Family BATHYERGID^. 



Genus HETEROCEPHALUS Riippell. 



1842. Eeterocephalus Rupprll, Mus. Senckenberg, vol. 3, Heft 2, p. 99. {H. 

 glaber.) 



In addition to the species of the naked mole-rat known from Somali- 

 land and Abyssinia, three forms have been described from British 

 East Africa. These species or subspecies have been based on single 

 specimens or very small series. After study of a suite of twelve speci- 

 mens from one general region — the Northern Guaso Nyiro — I find 

 that the characters used to separate these forms from Ileteroceylialus 

 glaber are all accounted for by individual variation. Skulls of Heteroce- 

 vlialus are subject to a remarkable amount of variation. (See pis. 6 

 and 7) In the series of specimens mentioned the differences in size 

 (usually accounted for by age) ; the variations in the form and posi- 

 tion of the posterior border of the bony palate, in the shape, size, and 

 relative position of the palatine foramina, and in the development 

 of the coronoid process are great, and cover virtually all of the con- 

 ditions described of the type-specimens of the named forms from 

 British East Africa. Remarkable variations in relative size and 

 shape of the molariform teeth are apparent in every specimen, and as 

 great variation is present in width and bulk of the incisors. One 

 skull in the collection, from Archer's Post on the Northern Guaso 

 N3dro, agrees almost to the slightest detail in every measurement 

 but one with the type skull of glaber as described by Thomas.^ The 

 single case of discrepancy in size is in the breadth of palate inside m? 

 and there is every reason to suspect that a mistake has been made in 

 recording that measurement in Mr. Thomas's account. Without a 

 suitable series of authentic skulls of glaber it will of course be impossi- 

 ble to settle the matter but it seems best to disregard the names 

 applied to specimens from northern British East Africa until such 

 actual comparison can be made. The type localities of the three 

 names in question are sufficiently close together so that, considering 

 the uniform conditions of local environment necessary to the life of 

 the animal, it is reasonable to suspect that only one form is repre- 

 sented. ]Mr. Heller compared this series of skulls with the material 

 in London and has noted on the label of one of the larger specimens 

 (No. 184171) that it is identical with skulls oi glaber from Somaliland; 

 and on the label of one of the smaller skuUs (No. 184176) that this 

 specimen is identical with the type skull of ansorgei. RuppeU's 

 figure of the type skull of glaber and the outline drawing of the same 

 specimen pubfished by Thomas in 1885^ do not agree in essential 

 details, and it is probably safest not to trust either for fine specific 

 comparisons. 



1 Proc. Zool. Soc. London, 1885, p. 848. s Proc. Zool. Soc. London, 1885, pi. 54, fig. 5. 



