KEY TO LAND MAMMALS OF NORTHEASTERN NORTH AMERICA 99 



triangles; form slender; tail long and hairy: eyes and ears large; fur soft. 

 (Ne 6 torn a; Gk., new cutter) 



The genus N e o t o m a is peculiar to America. It reaches its greatest 

 development in Mexico and the southwestern United States, where 

 70 or more forms occur. One species only is found in the eastern 

 United States north of the lower austral zone. This is a member of the 

 restricted Subgenus Neotoma, in which the tail is round. 



Neotoma pennsylvanica Stone Alleghany cave rat 

 1894 Neotoma pennsylvanica Stone, Proo. aoad. nat. sci. Philadelphia, 

 p. 16. (South mountain, Cumberland co. Pa.) 

 Grayish above, white beneath, tail furry, sharply bieolor. Total length, 410 

 ■(16i); tail vertebrae, 85 (7|); hind foot, 42 (J.H). (pennsylvanica; N. 

 Lat., Pennsylvaniail) 



The Alleghany cave rat is common in caves and rocky woods through- 

 out the Alleghanies. Its northern range extends to the lower Hudson 

 valley. This is the common rat in Mammoth cave. Aside from the 

 character of its teeth, the cave rat differs from the house. rat in its larger 

 eyes and ears, long soft fur and more hairy tail, which is dark above 

 anil white below, the two colors sharply defined. 



Genus Synaptomys Baird 



1857 Synaptomys Baird, llamm. N. Am. p. 558. Type Synaptomys 

 c p e r i Baird 

 Face of each upper front tooth ivith a distinet longitudinal groove, grinding teeth 

 without roots (prongs) ; skull small, not strongly angular; claws smaZZ, simple ; 

 tail moderate (about as long as hind foot) covered with short hairs; color always 

 <iark. (Synilptomys; Gk., connecting mouse) 



The genus Synaptomys, containing the smallest and least special- 

 ized of the lemmings, has not been detected in the old world. It is 

 generally distributed throughout boreal North America. Eight species 

 are now recognized, four of which occur within our limits. 



SPECIES OF SYNAPTOMYS 



Mammae 6 ; crown of each lower cheek teeth with a small closed 

 triangle of enamel on outer side (subgenus Synap- 

 tomys) 



Upper front teeth relatively broad and heavy S. cooper i 



Upper front teeth relatively narrow and light S. fatuus 



JMammae 8 ; crown of lower cheek teeth without closed triangles 

 of enamel on outer side (subgenus Mictomys) 



Total length, 115 (4i) S. innuitus 



Total length, 132 (5i%) S. sphagnicola 



