KEY TO LAND MAMMALS OF NORTHEASTERN NORTH AMERICA JJ 



Female without external pouch for carrying the young, 

 Eutheria (in species found within our limits, 

 tail never prehensile, teeth less than 50, innermost 

 toe of hind foot never thumb-like) 



Fore limbs modified to serve as wings (bats) Chiroptera, p. 146 



Fore limbs not modified to serve as wings 



Toes armed with hoofs (bison, deer etc.) Ungulata,p. 78 



Toes armed with claws 



Front teeth chisel-shaped and separated from 

 grinding teeth by a wide space (gnawing 



animals) Glires,p. 83 



Front teeth not chisel-shaped, tooth row essen- 

 tially continuous 

 Brain large, well developed; in species found 

 within our limits, size large, length 300 

 (12) to 2400 (96), eyes well developed, 



muzzle not greatly elongated (flesh-eaters) Ferae, p. 119 



Brain small, not highly developed; in species 

 found within our limits, size small, length 

 under 250 (10), eyes small or rudiment- 

 ary, muzzle greatly elongated (moles, 

 shrews, etc. ).. Insectivora, p. 140 



Order Marsupialia Marsupials 



Two small separate bones projecting from front of pelvis; female repro- 

 ductive organs double through greater part of their length ; young not attached 

 to parent before birth by a complicated special organ (placenta) but born in a 

 very undeveloped condition and carried for some time in an external pouch 

 of skin in which are situated the nipples; brain very small and simple; in 

 North American species tail prehensile, teeth 50, hind foot with five toes, the 

 innermost of which is clawless and thumb-like. (Marsupialia; Lat., a pouch) 



The order M arsupialia reaches its greatest development in Aus- 

 tralia and the neighboring islands. Elsewhere it is confined to South 

 America and the warmer parts of North America. Eight families are 

 recognized, six of which are peculiar to the Australian region. The 

 other two are confined to America. One of them rea'ches our limits. 



Family Didelphididae Opossimis 



Teeth 50 ; toes five, distinct, each provided with a well developed claw except 

 the first on hind foot, which is thumb-like and clawless. Tail long, prehensile, 

 mostly naked and scaly. (Didelphididae ; genus Didelphis) 



