68 ZOOLOGY OF THE VOYAGE OF THE BEAGLE. 



sides of the body, white ; hairs of the back palish gray at the base, those of 

 the belly indistinctly tinted with very pale gray at the roots ; ears and 

 moustaches pale brown. 



Habitat, New South Wales. 



Mus Rattus and Mus 



and is remarkable for its delicate colouring. The molar teeth are figured in Plate 

 34; fig. 18. a, represents the molars of the upper jaw, and fig. 18. b, those of the 



lower. 



Genus-REITHRODON.* 



Denies primores f ; inferioribus acutis, gracilibps, et antice lavibus ; supenonbus 



gracilibus, antice longitudinaliter sulcatis. 

 Molares utrinque f radicati ; primo maximo, ultimo minima : primo superiore plicas 



vitreas duas externe et interne alternalim exhibente ; secundo, et tertio, plicas duas 



externe, interne unam : primo inferiore plicas vitreas tres exteme, duas interne ; 



secundo, plicas duas externe, unam interne; tertio unam externe et interne, ex hi- 



J)SflttOUS • 



Artus incequales : antipedes \-dactyli, cum pollice exiguo :. pedes postici 5-dactyli, 



digitis externis et intemis brevissimis. 

 Ungues parvuli et debiles. Tarsi subtiis pilosi. 

 Cauda mediocris, pilis brevibus adpressis instructa. 

 Caput magnum, fronte convexo : oculis magnis : auribus mediocribus. 



The present genus according to my views belongs to the family Muridce. The 

 modifications of structure which have led me to separate it from the genus Mus 

 are as follows : 



External characters. - The most conspicuous points of distinction between the 



Mus (if we regard M . rattus, M 



M 



form of the head, the large size of the eyes, the stout form of the body, and 

 the upper incisors being grooved. The ears, tail and feet are more densely 



* PeeApoe, a channel ; Otov, a tooth. 



