MICROTUS 719 



no constant character in the enamel pattern by which they may 

 be distinguished. In the specimens examined the terminal loop 

 of m 3 is invariably short and broad, not showing any tendency to 

 the elongation occasionally occurring in M. nivalis. ■ 



Remarks. — Microtus lebrunii is represented by two geographic 

 races, one of which is remarkable, in the sub-genus Ghionomys, for 

 its occurrence at a distance from mountains and in a region of 

 unusually high summer temperature. 



Microtus lebrunii lebrunii Crespon. 



1844. A[rvicola] lebrunii Crespon, Paune Meridionale, i, p. 77. 



1857. Arvicola nivalis b. Arvicola leucurus Blasius, Saugethiere Deutsch- 



lands, p. 359 (part). 

 1908. Microtus lebrunii lebrunii Miller, Ann. and Mag. Nat. Hist., 8th ser., 



I, p. 101, January, 1908. 

 1910. Microtus (Chionomys) lebruni Trouessart, Faune Mamm. d'Europe, 



p. 184. 



Type locality. — Neighbourhood of Nimes, Gard, France. 

 Altitude, 180 m. 



Geographical distribution. — Known with certainty from the 

 type locality only, but probably extending through the Cevennes 

 and the mountains of Auvergne. 



Diagnosis. — Back clear, very pale smoke-grey, without evident 

 wash of wood-brown ; skull with auditory bullae small and 

 flattened. 



Colour. — Upper parts a very pale smoke-grey with a faint 

 bluish tinge, particularly on neck and between ears, the back 

 faintly "lined" with black, the sides and rump nearly clear; 

 underparts buffy white, not sharply defined, the slate-black under 

 colour appearing irregularly at surface and producing a bluish 

 tinge ; sides of muzzle dull white ; feet and tail white 

 throughout. 



Skull. — Auditory bullae decidedly reduced in size as compared 

 with those of M. nivalis, so that the lower edge of bulla scarcely 

 extends beyond line of cutting edge of molars. 



Measurements. — Three adult males from the type locality : 

 head and body, 117, 121 and 122 ; tail, 56, 55 and 66 ; hind 

 foot, 18-6, 19-6 and 18-8 ; ear, 13, 14-2 and 14. For cranial 

 measurements see Table, p. 721. 



Specimens examined. — Six, all from the neighbourhood of Nimes (B.M., 

 Mottaz and Nimes) ; no exact locality, 2. 



Bemarhs. — This animal presents the anomaly of a member of 

 the nivalis group completely adapted to life in the hot dry plains 

 of south-central France, a region where its presence can in no 

 way be explained as due to special local conditions. A mounted 

 specimen in the Paris Museum collected in Auvergne (probably 

 near QJermont-Ferrand) by Lecoq, and presented in 1854, is 



