696 DE. c. I. roESTTH iLUOB ois^ THE [June 1, 



group of muriform Eodents (Muridce, auet.), o£ which they are 

 the lowest of existing forms, having aftinities witli some of the 

 least specialized of the family Dipodidae, as defined by Winge, 

 viz. with Sminthus and Zapus." It was further pointed out that 

 the African and Asiatic Jihizomyes (Tachi/oryctes and Bhizomys) 

 present relations with the Malagasy Eodents, and that the affinity 

 is especially close betv%een Tachyoryctes and Brachyuromys rami- 

 rohitra. 



In the present paper I propose to give a fuller description of 

 the skull and dentition of the two species of Brachyuromys, and to 

 compare them with those Eodents outside Madagascar with which, 

 in my opinion, they have affinities. The description of the other 

 Malagasy Muridee must be postponed to a future paper ; but I 

 shall have to refer to them repeatedly in the following pages. 



Genus Beachyubomts, Maj. 



Skull broad and massive. Upper profile of cerebral cranium 

 flattened. Supraorbital crests rounded off. Incisors and rooted 

 semihypselodont molars (gi^g) large as compared to the size of the 

 skull. Infraorbital foramen large, but on the whole with the 

 shape characteristic of Muridse. Jugal large and approaching 

 the lachrymal. Transverse diameter of incisors exceeding the 

 longitudinal '. Crowns of molars flattened, not tuberculate ; 

 unworn molars of species 2 half-tuberculate. In young speci- 

 mens the crowns of the molars show three lobes of enamel, 

 united by cement and obliquely disposed (inclining forwards with 

 iheir outer portion), the posterior lobe in the upper, the anterior 

 one in the lower molars being the smallest. These lobes soon 

 unite together, producing various patterns, hy which the different 

 species may be easily distinguished. Tail shorter than usual in 

 Muridae. 



By their broad, moderately flattened, roundish heads and 

 comparatively short tails these Eodents recall somewhat the Voles 

 in outer appearance. 



1. Brachxuromts eamieohttea, Maj. (Plate XXXVII. fig. 2 

 and Plate XXXIX. figs, l-d.) 



Ears large, oval. Coloration of upper parts brown, abundantly 

 mixed with black, on the sides less dark, the black hairs gradually 

 diminishing. Lower parts fawn. Bases of hau's slate-coloured. 

 Tail fui'nished above with black, beneath with grey hairs. 



Parietal crests diverging anteriorly. Interparietal short in 

 transverse, but longer in antero-posterior diameter than in B. betsi- 

 leoensis. Molars very large, all about of equal size and pattern, 

 the third in both jaws generally slightly smaller than the other 



^ (1) Where the incisors are wider than thick, the gnawing habit is feebly 

 clcTeiopeci. — (2) Where the incisors are thicker than wide, the gnawing habit 

 is greatly developed (Ryder, " The Significance of the Diameters of the Incisors 

 in Rodents," Proc. Acad. Nat. Sci. Philadelphia, 1877, pp. 314-18). 



