230 RODENTIA. 



Hesperomys, sp. 2. 

 Hob. S. America. 



17616 a. Anterior portion of the cranium, and two rami of the 

 mandible ; from the caverns of Minas Geraes, Brazil. This 

 cranium is smaller than the last, and has not been identified 

 with that of any living species. 



Claussen Collection. Purchased, 1845. 



Hesperomys, sp. 3. 

 Hob. S. America. 



18898. Middle portion of the cranium, showing the cheek-teeth; 

 from a cavern in Minas Geraes, Brazil. The teeth of 

 this species are larger than those of the last. It comes 

 nearest to the group Oxymycteris. 



Claussen Collection. Purchased, 1845. 



Hesperomys, sp. 4. 

 Hab. S. America. 



18897. Anterior portion of the cranium, showing all the dentition; 

 from a cavern in Minas Geraes, Brazil. This specimen 

 belongs to the group Halrotlirix, and comes nearest to the 

 existing H. arviculoides, Pictet. 



Claussen Collection. Purchased, 1845. 



B. Molars semirooted or rootless. 

 Genus ARVICOLA, Lacepede 1 . 



Molars rootless (rarely semirooted), separated into prisms, which 

 are placed alternately. 



ilrbtcola ampfitfriuS (Linn. 2 ). 

 Syn. Mus amphibius, Linn. 8 



Four outer and five inner angles in first lower molar ; three outer 

 and two inner angles in second upper molar; molars rootless 

 throughout life. 



Hab. Europe and North Asia. 



15081. Anterior portion of the cranium and three imperfect rami of 



(Fig.) the mandible ; from Kent's-Hole Cavern, Torquay. The 



cranium and one ramus of the mandible are figured by 



Owen in the Brit. Foss. Mammals and Birds, p. 201, fig. 76. 



McEnery Collection. Purchased, 1842. 



1 M6m. de I'lnstitut, vol. iii. p. 495 (1801). 



1 Syst. Nat. ed. 12, vol. i. p. 82 (1766), Mus. 3 j^ cit 



