246 KODENTIA. 



Ctenomys, sp. 2. 

 Hob. S. America. 



40675 b. The associated cranium and mandible, in a somewhat 

 broken condition; from the Pleistocene of -Buenos Ayres. 

 These specimens, which indicate a smaller species than 

 the last, come very close to the existing C. leucodon. 



Bravard Collection. Purchased, 1854. 



Family HYSTRICID^. 



Dentition : I. \, C. J, Pm. \, M. |. 



Genus SYNETHERES, F. Cuvier '. 



Syn. Sphingurus, F. Cuvier 2 . 

 Cercolabes, Brandt 3 . 



The teeth of this genus can only be distinguished from those of 

 Erefhizon by the circumstance that in the latter the first tooth of 

 the cheek-series is considerably longer than the last, whereas in the 

 former all the teeth are subequal. 



Synetheres fossilis (Waterhouse 4 ). 



Syn. Cercolabes fossilis, Waterhouse 6 . 

 (?) Synetheres magnus, Lund 8 . 



As the remains on which this species is founded do not show the 

 first tooth of the cheek-series, it is impossible to say whether it 

 really belongs to Synetheres or Erethizon. On distributional grounds 

 it is, however, more probable that it belongs to the former, to which 

 it is accordingly provisionally referred. In size it considerably 

 exceeds the existing Erethizon dorsatus, and is therefore very much 

 larger than any of the existing species of Synetheres. 



Hob. S. America. 



18869. Two fragments of the opposite rami of the mandible : from 

 the caverns of Minas Geraes, Brazil. The more perfect 

 specimen shows the three true molars, and the less perfect 



1 M6m. d. Mus6um, vol. ix. p. 413 (1822), Synethere. 



2 Loc. cit., Sphingure. 



3 M6m. Ac. Imp. St. PStersbourg, ser. 6, vol. iii. p. 391 (1835). 



4 Natural History of the Mammalia, vol. ii. p. 436 (1848), Cercolabes. 

 " Loc. cit. 



K. Danske Vid. Selsk. Skr. vol. vii. p. 250 (1840). 



