AMERICAN BATS OF THE GENERA MYOTIS AND PIZONYX 13 



occur in either the British Islands or Japan, a fact which may indi- 

 cate that they are more sedentary in habit than some of their smaller 

 relatives. 



That the American Myotis stock came originally from the north- 

 ern part of the Old World is made to appear probable by the follow- 

 ing circumstances : The greater variety and higher degree of differ- 

 entiation among the Palearctic members of the genus, an indication 

 of greater age for this portion of the group; the occurrence of the 

 greatest number of American species in western North America, the 

 region nearest the supposed Asiatic source of supply; and finally 

 the diminution in number of species as we go away from this western 

 region, either toward the east or toward the south. 



Three North American species of Myotis have geographical 

 ranges which extend across the continent from ocean to ocean. They 

 are M. lucifugus with a north-south distribution from tree limit to 

 southern Mexico, M. keenU ( = the subulatus of H. Allen and recent 

 authors) with a range from the southeastern United States to British 

 Columbia and southern Alaska, and M. suhidatics (of Say) prac- 

 tically confined to the United States. All of the others are restricted 

 either to the East or to the West. 



North America east of the Mississippi is inhabited by three species 

 peculiar to the region, all of them rather imperfectly known as to 

 details of distribution, though structurally they are well differenti- 

 ated from each other and from the three wide ranging types which 

 occur with them. One of these, 31. grisescens, appears to be peculiar 

 to the limestone cave region of the central and southern United States, 

 another, also apparently a cave bat, M. sodalis, has been found in the 

 Southern States and in Vermont, while the third, M. austroripariiis, 

 Las been observed in only two regions, one in Indiana and the other 

 on the west coast of Florida. 



In contrast to the eastern United States, western North America, 

 the portion of the New World nearest the supposed Asiatic center of 

 dispersal, has no less than eight species not yet known to occur else- 

 where. One of these (milleri) has thus far been collected at a 

 single locality only, in Lower California; the others have wide and 

 well-defined ranges in the region west of the plains. Four of these 

 {calif omicus, evotis, volcms, and yunianensis) extend from the north- 

 west coast region to southern Mexico, two {thysanodes and velifer) 

 do not range so far to the north, while the remaining species, occultus, 

 still imperfectly known, appears to be restricted to the southwestern 

 United States and the adjoining parts of Mexico. 



Of the five species definitely known to inhabit South America, 

 three, chiloensis, nigricans, and i^her, are generally distributed and 

 not strongly differentiated from each other. Their nearest relatives 

 to the north appear to be M. lucifugus and M. yvjmanensis. Prob- 



