MICBOTUS. 429 



A. Molars rootless, elongate, composed of prisms. 



a. Ear-conch present MICROTUS. 



b. Ear-conch wanting ELLOBIUS. 



B. Molars rooted, tubercular CRICETUS. 



Genus MICROTUS, Schrank (1798). 



Syn. Arvicola, Lacepede (1801) ; Hypudeeus, Illiger (1811) ; Neodon, 

 Hodgson (1849) ; Phaiomys, Blyt'h (1863). 



Head short, rounded ; ears, tail, and limbs short. Fur soft and 

 thick. The thumb (pollex) is short and sometimes clawless, more 

 often it bears a short compressed claw. Nasal portion of skull 

 short ; brain-case oval, broad, and depressed ; infraorbital foramen 

 of the typical marine form ; anterior palatine foramina long ; 

 interparietal large, pointed in the middle anteriorly; auditory 

 bullae moderately large. Incisors orange or yellow, flat in front ; 

 molars rootless, formed of subtriangular prisms biserially arranged, 

 with sharp salient angles on each side, the number varying in the 

 different species. The last upper and first lower molars vary 

 more than the others. 



The genus is Palsearctic and Nearctic, several species inhabiting 

 the higher Himalayas. Of these I published a detailed account in 

 1881 (J. A. S. B. 1, pt. 2, p. 88). From that account the following 

 descriptions are abridged. 



Synopsis of Indian and Burmese Species. 



A. Thumb of fore foot clawless. . 



. Colour light ferruginous brown M. stoliczkanus, p. 430. 



b. Colour light brown, with a grey tinge. . M. stracheyi, p. 431. 



B. Thumb with a small claw. 



a. Ears not projecting beyond the fur. 



a. Colour dark rich brown above, light 



brown below M. ivynnei, p. 431. 



b'. Colour rufescent brown, lower parts 



light brown M. roylei, p. 430. 



c'. Colour earthy brown, lower parts 



whitish. M . blythi, p. 432. 



b. Ears projecting beyond the fur. 



a'. Colour light greyish rufescent brown ; 



tail i head and body M. blanfordi, p. 432. 



b'. Colour dark yellowish brown ; tail 



head and body 

 a". Ear from orifice 0'5 in. ; anterior 



lower molar with 6 internal angles M. sikimensis, p. 433. 

 b". Ear from orifice 0'35 in. ; anterior 



lower molar with 5 internal angles M. melanogaster, p. 434. 



Of these species, M. blythi, M. siTcimensis, and M. melanoyaster 

 differ from all the others in the form of the molar teeth, and the 

 two last named differ greatly from M. blythi. In the remaining 

 five species the posterior upper molar terminates behind in an 



