238 Mr. O. Thomas on African Mole-Rats. 
species so much as to have different planes of cleavage of the 
egg, a different derivation of the germ-layers, and a different 
mode of formation of the gut. Nor do I think its egg and 
embryo are symmetrical before the germ-layers are differen- 
tiated. 
In his accurate study of the cell-lineage of Unio, Mr. Lillie 
finds that each of the cells of the four-cell stage contains 
entodermal elements. In the marine forms the derivation of 
the entoderm from the large macromere alone is interesting, 
since in the early stages of cleavage the lineage of the cells 
in the various Pholadide is so like that in Unio, even to 
minute details. 
XXXV.—On African Mole-Rats of the Genera Georychus 
and Myoscalops. By OLDFIELD THOMAS. 
I. A new Species of Georychus from Mashonaland. 
THE arrival of two small collections of admirably prepared 
skins from Mazoe and Salisbury, Mashonaland, presented 
respectively by Mr. J. Ffolliott Darling and Mr. Guy A. K. 
Marshall, in each of which there are two specimens of a 
Georychus, has involved the re-examination of the Museum 
material in that genus. Of the species found in Angola 
Prof. Barboza du Bocage has recently given an account*, 
dividing them into several groups or forms, which he wisely 
does not venture to define specifically, both on account of 
their exceeding difficulty and for want of better material 
than is as yet possessed by any museum. The South-African 
ones, however, are perhaps more easily arranged, at least 
provisionally, for instead of the considerable number of 
different forms found in Angola there seem to be only three 
or four altogether, and these well separated geographically. 
Thus, G. capensis of the western Cape Colony is perfectly 
distinct from the others, while all the specimens from the 
eastern part of the colony, from Natal northwards to the 
Limpopo, seem fairly referable to G‘. cwcutiens, from which 
I cannot at present distinguish G. hottentottus, Less., G. Lud- 
wigt, A. Sm., or G. holosericeus, Wagn.t North-westwards 
* J. Sci. Lisb. (2) iv. p. 269 (1890). 
+ This species was founded on three specimens from different localities 
which might hereafter prove to be of different species; but as Graaf 
Reinet is the first-mentioned locality, the one from there should be taken 
as the type. 
