720 ON THE MALAGASY GEITUS BEACHTimOMTS. [June 1 , 



Brachyuromiis &c., I. e. the preservation of primitive types of 

 Muridcp \ Theirs is a parallel to that of the African insecti- 

 vorous family Chri/sochloiida', as compared with the more generalized 

 memebrs of the Malagasy family Centetklcp. 



Whilst the somewhat closer agreement with Brachyuromys 

 than with the rest of Malagasy Eodeuts may in the case of 

 Rhizomi/s, SjJctJa.v, and Sijyhneus be due to the circumstance that 

 in each the molars are hypselodont (though in a much lesser degree 

 in Brachynromys), the case seems to be different with regard to 

 Tachyoryctes. This latter is in the pattern of its molars almost 

 identical ^ith one of the species of BracJiyuromys (B. ramirohitra). 



The mutual relations of the Hesperomyina, Microtinai, MwincB, 

 and Spalacidte with each other and with the Malagasy jS'esomyince 

 have thus to a certain extent been cleared up by a better ac- 

 quaintance with the latter. 



EXPLANATION OF THE PLATES. 



Plate XXXVH. 



Fig. 1. Skull of Brachyurow.ys betsileoensis (Bartl.) : fig. 1, side view ; 1 a, from 

 below ; 1 b, from above ; 1 c. front view. 



2. Skull of £. ramirohitra. Maj.: fig. 2, side view ; 2a, from below; 



2 b. from above ; 2 c, front view : 2 d, side view of mandible. 



3. Skull of Tachyoryctes splcndens, Eiipp. : fig. 3, side view ; 3 a, from 



below ; 3 b, from above ; 3 c. front view. 

 All figures nat. size. 



Plate XXXVIII. 



Difierent views of the skull of Bhi-omys sineiisis, Gray. Nat. size. Fig. 1, 

 side view ; fig. 2, from above : fig. 3, from below ; fig. 4, from behind ; 

 fig. 5, oblique view of left infraorbital foramen ; fig. 6, postero- 

 superior part of left mandible, from behind. 



Plate XXXIX. 



Figs. 1 a-8 a. Upper molars of Brachyuromys and Tachyoryctes, enlarged. 



1 6-8 b. Lower molars of ditto. 



1 (Z-3 b. Brachyuromys ramirohitra, Maj. 



4 a-4 b. Tachyoryctes annectens, Thos. 



5 a-6 b. T. splendens, Eiipp. 



7 a-8 b. Brachym-omys betsileoensis (Bartl.). 



Plate XL. 



Figs. 1 a-la. Upper molars of various species of Rhizomys, enlarged. 

 1 6-9 6. Lower molars of ditto. 

 1 a-3 6. Rhizomys badius, Hodgs. 



4 a, 46. R. pruinosus, Blyth. 



5 a-6 6. R. sumatrensis (Rafiles). 

 7 a-8 b. R. sinensis, Gray. 



9 6. R. sivalensis, Lyd. 



1 Still more striking instances amongst Rodentia of adaptation as a pre- 

 server of primitive types are afforded by the Aplodontida and the Leporidcs, 

 both of them very primitive Eodent families showing the curious combination 

 of some very specialized features with their primitive characters. 



