320 MAMMALIA t GLIKES. XLVIII. 



short, ears small). A large sub-family, Northern Hemisphere, many 

 species, including the lemmings, polar. (Microtinos.) 

 b. Tail flattened, scant-haired; hind feet partly webbed. . . . FIBER, 542. 

 bb. Tail subterete. 



c. Upper incisors grooved SYNAPTOMYS, 543. 



cc. Upper incisors not grooved. 



d. Molars rootless from persistent pulps MICKOTUS, 544. 



dd. Molars rooted, small and weak (back red). . . EVOTOMYS, 545. 

 ddd. Molars rooted, large and strong (back not red) PHKNACOMYS, 546. 

 aa. Incisors narrow, compressed ; molars rooted, tuberculate, with crenate mar- 

 gin (body slender; eyes and ears large; snout pointed; motions rapid). 

 e. Molars of upper jaw with tubercles in two series (American species). 

 f. Mouse-like. (Cricetince.) 



g. Upper incisors grooved. . . . REITHRODONTOMYS, 547. 

 gg. Upper incisors not grooved. 



h. Tail scant-haired, very long, as long as head and body; ears 



very small ORYZOMYS, 548. 



hh. Tail closely haired, much longer than head; ears large. 



PEROMYS<?IJS, 549. 



hhh. Tail closely haired, scarcely longer than head. 



ONYCHOMYS, 550. 

 ff. Ratlike, molars with re-entrant angles; length, with tail, a foot 



or more. (Neotomince.) NEOTOMA, 551. 



ee. (Molars of upper jaw, with tubercles in three series; soles naked; 

 tail long, scant-haired or scaly (Murinos ; old world species, introduced 

 in the United States) Mus. 



542. FIBER Cuvier. (Lat., beaver.) 



1039. F. zibethicus (L.). MUSKRAT. Color dark brown. 

 L. 22|. T. 11. E. N. Am. ; everywhere. Largest of our Muridce ; 

 building houses or burrows about streams and ponds. (Lat., 

 zibetha, the Civet, from the odor.) 



1040. F. macrodon Merriam. Color very much darker; 

 teeth very much larger, others like the common muskrat. Dismal 

 Swamp, Va. (/xafcpos, large; oSous, tooth.) 



543. SYNAFTOMYS Baird. (o-waTrrto, to join ; /iCs, mouse ; 

 connecting lemmings and mice.) 



1040. S. cooperi (Baird). LEMMING MOUSE. Mouse-color, 

 grayish below ; head very large with long whiskers ; fur soft and 

 long. L. 4|. T. I-. Minn, to Mass., S. to mts. of N. C., a remark- 

 able animal, between the field-mice and the lemmings (Zemmws). 

 (To William Cooper of Hoboken, N. J.) 



1041. S. fatuus Bangs. Similar to . cooperi, but with much 

 narrower upper incisors ; the skull smaller. Quebec, N. B., Me., 

 and N. H. (Lat., foolish.) 



1042. S. helaletes Merriam. Size of 5. cooperi, larger fore 



