62 Mcrridin — Geo(jr<ij)hi<- Didrihutujn of Life. 



Cervus ("uniculus 



Rangifer Lagomys 



Aloe Vnl2:)es 



Ovis Frsus 



Bison Thalarftos 



Tan lias Latax 



Arctomj's Lntreola 



Castor I'ntorius 



Phenaconiys .Mnstela 



Evotomys (tuIo 



Arvicola So rex 



Myodes Crotrichns * 



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

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

 also common to the two continents : 



Scinropterus Fells 



Sciurus Lynx 



SpermopliUns Vesperugo 



Lepus VespertUio 



Canis Plecotnsf 



Lutra Nyctinonins 



Most of these genera are known to be of great anti(|uity, their 

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

 that the others lielong to the same category, liut have thus far 

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

 attain their maximum development and numbers in the vSonoran 

 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 re])resentative3 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 [/. e., Sono- 

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



■■'As stated above, Flower and Lydckker do not recognize the American 

 animal as generieally distinct from I'mtrirlinx. Wliile I agree with Dob- 

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

 of groups, to bring together such closely related types. 



tTlic American species of Plpcohm are separated generieally ))y Dr. 

 Harrison Allen under the name (hri/norhitrits, which is adopted by the 

 writer. The more compndiensive name Plecolus is here used for the rea- 

 son just stated under I'nilr'K-lmx. 



