CLASSIFICATION OF VERTEBRATA 43 



with the calcaneum. Tibia and fibula separate. Narrow 

 infraorbital canal. 



Leporidae. Palaeolagos. Lower Miocene, U.S.A. 



Lepus. Since Miocene ; cosmopolitan, excluding 



Australasia. 



Lagomys. Periarctic ; since Miocene. 

 HYSTRICOMORPHA, Brandt. Incisors ^. Wide infra- 

 orbital canal. Tibia and fibula separate. 



Hystricidae. Periarctic, Ethiopian, neotropical. 



Hystrix, Erethizon. Since Miocene. 

 Dasyproctidae. Neotropical. 



Dasyprocta, Coelogenys, Dinomys. 

 Octodontidae. Neotropical. 



Octodon, Myopotamus, Capromys. 

 Ethiopian : Aulacodus. 

 ?Theriodomys. Eo- and Miocene, Europe. 

 Caviidae. Neotropical : Cavia, Hydrochoerus, Dolichotis. 

 Chincliillidae. Neotropical : Chinchilla, Lagostomus. 

 ? Castoroides. Plistocene. North America and Antilles. 

 ? JEocardidae. Tertiary, Patagonia. 



SCIUROMORPHA, Brandt. Incisors ^. Infraorbital canal 

 small. Tibia and fibula separate. 



Cosmopolitan, excluding Australian region. 

 Sciuridae. Sciurus, Arctomys, Tamias, Pteromys, Haplo- 

 don, etc. 



Sciuroides. Eocene, Europe. 

 Anomaluridae. Ethiopian : Anomalurus. 

 Castoridae. Periarctic, since Miocene : Castor. 

 MYOMORPHA, Brandt. Incisors ^. Infraorbital canal wide. 

 Tibia and fibula fused. Since the Oligocene. Cosmopolitan. 

 Myoxidae. Since Eocene, now palaearctic and Ethiopian. 



Myoxus, Muscardinus. 



Muridae. Cosmopolitan : Mus. Periarctic : Arvicola. 

 Palaearctic and palaeotropical : Gerbillus, etc. Periarctic and 

 neotropical : Cricetus, etc., since Miocene. 

 Madagascar : Hypogeomys, Nesomys. 

 Australian : Hydromys, Hapalotis. 



Spalacidae. Palaearctic and palaeotropical, excluding 

 Madagascar : Spalax, Khizomys, Heterocephalus. 



