52 



Bibliographical Notices. 



supra dilatatum, infra angustatum ; mandibulse angulus rotun- 

 datus, denies primores inferiores acuminati. 



a. Molares f . 

 Hydromys. 



b. Molares f. 



a. M.tuberculati, /3. M.plani, opposite y. M.altematira incisi. 



incisi. 



Mus. 



Cricetus. 



Dendromys. 



Akodon. 



Hapalotis. 



Pseudomys. 



Mystromys. 



Rhombomys. 



Psammomys. 



Merioncs. 



Euryotis. 



' Sigmodon. 

 Neotoma. 

 <( Elbnodon. 

 £ j Reithrodon. 

 l« [^Cte7iodactylus. 



r§ r My odes. 

 '"o < Hypudaus, 

 I IFiber. 



ft- 



M. plani, incisi. 

 Saccomys. 



c. Molares f . 

 Stninthis. 



d. Molares |. 

 a. M. tuberculati. 



Perognathus* . 

 Distributed over the whole earth. 



IX. Castoeina. Corpus robustum, magnum, pedes 5-dactyli, pos- 

 teriores palmati ; dentes primores validi, cestiformes, molares f 

 complicati, latere altero triplicati, altero implicati. 



Castor, Myopotamus. 



Geog. distr. Northern & temperate districts of Old & New World, 



Myopotamus belongs to the southern half of South America. 



X. Hystricina. Corpus aculeis teretibus validis, setis intermixtis 



vestitum; foramen infraorbitale maximum; claviculae incompletae ; 

 dentes molares ^ complicate 



a. Philogsea. /3. Philodendra. 



Hystrix. Erethizon. 



Athernra. Cercolabes. 



(Synetheres and Sphiggui'ns .) 

 Southern Europe, Asia, Africa and America. 



XI. SuBUNGULATA. Corpus piUs tectum, cauda brcvissima aut uulla, 

 ungues subunguljeformes, foramen infraorbitale permagnum, 

 claviculse incompletse, dentes molares ^. 



a. Molares complicati. b. Molares compositi. 



Dasyprocta. Hydrochcerus. 



Coelogenys. Cavia. 



Confined to South America. Kerodon. 



XII. DuPLiciDENTATA. Dcutcs primorcs superiores duplicati, foramen 

 infraorbitale parvum, foramina optica conjuncta, palatum osseum 

 singulariter coarctatum, claviculse partim incompletae, partim 

 completse. 



Lepus, Lagomys. 



Distributed over the whole earth with the exception of NewHolland. 



* Dtpodomys, Gray (see vol. vii. p. 521), will perhaps be placed here. 



