320 mammalia; gliees. — xlviii. 



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

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

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

 bh. Tail subterete. 



c. Upper incisors grooved Synaptomys, 543. 



CO. Upper incisors not grooved. 



d. Molars rootless from persistent pulps Miceotus, 544. 



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

 ddd. Molars rooted, large and strong (back not red) Phenaoomys, 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. . . . Reitheodontomys, 547. 

 gg. Upper incisors not grooved. 

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



very small Oeyzomys, 548. 



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



Peeomyscus, 549. 

 hhh. Tail closely haired, scarcely longer than head. 



Ontchomys, 550. 



ff. Eatlike, molars with re-entrant angles ; length, with tail, a toot 



or more. {NeotomincB.) ...... Neotoma, 551. 



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

 tail long, scant-haired orscaly (Murinw ; old world species, introduced 

 in the United States) Mus. 



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



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

 L. 22i. T. 11. E.N.Am.; everywhere. Largest of our il/unV(E ; 

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

 zibetha, the Civet, from the odor.) 



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

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

 Swamp, Va. (jiaKpos, large; oSous, tooth.) 



543. SYNAPTOMYS Baird. (<ruvdjTTa>, to join ; fiis, mouse ; 

 connecting lemmings and mice.) 



1040. S. cooperi (Baird). Lemmixg Mouse. Mouse-color, 

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

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

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

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



1041. S. fatuus Bangs. Similar to S. 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 S. cooperi, larger fore 



