492 Mr. 0. Thomas on 



of normal structure, a well-marked autero-external secondary 

 cusp on m'', as well as the usual large antero-iiitenial. 



Dimensions of the type : — 



Head and body (c.) 85 mm. ; tail \)0 ; hind foot (s. u.) 19; 

 ear 12 5. 



Skull: greatest length 21; basilar length 17'5 ; zygo- 

 matic breadth 12 ; nasals 8 ; interorbital breadth 3"7 ; breadth 

 of brain-case 11 ; palate length 10"1: ; diastema G'O; palatal 

 foramina 4'7 x 1'7 ; length of up})er molar series 3"4. 



Bab. Kobe, Hondo. Alt. .^00-400 m. 



Ti/pe. Male. B.M. no. 5. 3. 3. 37. Collected May 1904. 

 Presented by R. Gordon Smith, Esq. 



This pretty little mouse is quite unlike any Eastern Asian 

 species with Avhich I am acquainted. j\Ius anjenteus, Temm., 

 whose description might have been thought to apply to it, is 

 a larger animal, with a hind toot of 22 mm., and many differ- 

 ences in the detailed measurements of the skull, e. g. inter- 

 orbital constriction 4*9 mm., palatal foramen 5"8. 



With regard to the use of tlie generic name Micromys for 

 this animal, L have come to the conclusion that the correct 

 and natural division of the Euroj)ean s|)ecies of ''^ Mas" 

 ])ublished by Hensel in 1856 *, and supported by Forsyth 

 Mcijor t in 1884, should be followed, and that while J/us 

 rattus, norvegicus, and musculus should remain in J/u5, the 

 others should be placed in a separate genus, for which the 

 name Micromys is available. 



In this genus the posterior laminse of the first and second 

 upper molars have each an additional internal cusp beyond 

 the number present in Mus ; so that, counting along the 

 inner side of the tooth -row, there are three cusps on the first 

 molar and three on the second, while in Mas the posterior 

 lamina is not continued inwards beyond the centre, and there 

 are therefore only two inner cusps on each of the two teetli. 



The following species, with their respective near allies, 

 show this character: — 



Micromys sijlvaficus, L. 



speciosus, Temm. 



minutus, Pall. (Type of genus J.) 



mystacinus, Dant. & Alst. 



agrariiis, Pall. 



IJarti, Thos. 



geisha, Thos. 



* Zeitschr. deutsch. geol. Gesellsch. 1866, p. 281. 

 t Atti Soc. Tosc. Proc. \evh. iv. p. 129 (1884). 

 i Dehne, 1841. 



