62 Merriain Geographic Distribution of Life. 



Cervus Cuniculus 



Rangifer Lagoi 1 1 y s 



Alee Yuljx's 



Ovis Ostis 



Bison Thalarctos 



Tanrias La tax 



Arctomys Lutreola 



Castor . Putorius 



Phenacomys Mustela 



Evotomya Gulo 



Arvicola Sorex 



Myodes Urotriclms * 



In addition to the foregoing genera, which are clearly of Bo- 

 real origin, the following 12 genera of more extended range are 

 also common to the two continents : 



Sciuropterus Felis 



Sciurus Lynx 



Spermophilus Yesperugo 



Lepus Vespertilip 



Canis Plecotusf 



Lutra Nyctinomus 



Most of these genera are known to be of great antiquity, their 

 remains having been found in Miocene strata, and it is probable 

 that the others belong to the same category, but have thus far 

 escaped detection, owing to their very small size. All of them 

 attain their maximum development and numbers intheSononin 

 Region in America and the analogue of the Sonoran in Eurasia ; 

 but by reason of the great length of time that has elapsed since 

 they came into existence some of their representatives have be- 

 come acclimated to a wide range of climatic conditions. 



Dr. John L. Le Conte, in his report on the Coleoptera of Lake 

 Superior, said : " The entomologist cannot fail to be struck with 

 two very remarkable characters displayed by the insect fauna of 

 these northern regions. First, the entire absence of all those 

 groups which are peculiar to the American continent [/. c.. Sono- 

 ran and Tropical groups]. * * * The few new genera Avhich 



*As stated above, Flower and Lydekker do not recognize the American 

 animal as generically distinct from ri-ofi-irlutx. While I agree with Dob- 

 son in according it generic rank, it is convenient, in studying the origin 

 of groups, to bring together such closely related types. 



fThe American species of /'/eroftix are separated generically by Dr. 

 Harrison Allen under the name <'ni-ntnn-hinm<, which is adopted by the 

 writer. The more comprehensive name J'/trofii* is here used for the rea- 

 son just stated under Uro&nchtu. 



