On Gerbils referred to the Genus Meviones. 263 
XXVI.—WNotes on Gerbils referred to the Genus Meriones, with 
Descriptions of new Species and Subspecies. By OLDFIELD 
THOMAS. 
(Published by permission of the Trustees of the British Museum,) 
THE genus Meriones has long been in a very great state of 
confusion, partly owing to the carelessness of authors in 
lumping specimens from all sorts of localities together, and 
partly to the fact that the genus falls into groups distin- 
guishable only by the different sizes of their bulla, and that 
members of each of the groups may be found living side by 
side—so that a single district may contain two or three 
species, all looking so alike as to be readily confused with 
each other, and yet really distinguishable on close examina- 
tion. Thus no less than three species are found in Egypt, 
the very country where certain names have been overlooked 
or misapplied—so as to add to the general confusion. 
I have not been able to complete the work in any sense, 
but can make some preliminary observations on the habitats 
and characteristics of the different forms. 
The bull, whose structure and development give thie 
primary means of distinction, enable us to separate the species 
(apart from tie aberrant calurus and hurriane) into four 
groups, as follows :— 
(a) The bulle very large, the swelling in front of the 
meatus projecting in front of the level of the hindmost corner 
of the zygomata, and the suprameatal triangle also very 
large. Meatal length (¢. e. the distance from the back of the 
bulla to the front of the meatal swelling) approximately 
14-15 mm. 
(6) Bulle similarly large, but the suprameatal triangle 
comparatively small. (‘Tail usually more bushy than in other 
species. ) 
(c) Bulla smaller, the front side of the meatus little 
swollen, and not reaching to the level of the zygoma (meatal 
length about 11-12 mm.) ; triangle also small. 
(d) Bullee quite small for the genus, almost in normal 
proportion to the general size of the skull. (Meatal length in 
M. blacklert 8°2 mm.) 
In Algeria the confusion of the names is too great to clear 
up now, but as a preliminary it may be said that north of the 
Atlas we have true shawi (group c), which is represented on 
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