320 MA.MMA.LIAt GLIRES. — XLVIII. 



short, ears timall). A larpe Bub-familr, Northern Hemisphere, many 

 Ppecies, iiicludiiifc the lemiiiini;s, polar. (MicrulintB.) 

 b. Tail tiiittoncd, .scant-haired; hind feet partly webbed. . . . Fiueh, 542. 

 bb. Tail siibterete. 



c. Upper incisors grooved Synaptomys, 543. 



cc. I'ppor incisors not tjrooved. 



d. Molars riioiK-ss from persistent pulps Mickotcs, 544. 



dd. M'.lars rootod, small and we ik (back red). . . Evotomys, 545. 

 ddd. Molars rooted, la r{:;e :ind strong (hack not red) PiiKNAroMYS, 540. 

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

 gin (boil V slender; eyes and ears large; snout pointeil; motions rapid). 

 e. Molars of upper jaw wilh tubercles in Iwo series (American species). 

 f. Mouse-like. (CricrtincB.) 



g. Upper incisors grooved. . . . Reithroi>ontomys, 547. 

 90- Upper incisors not grooved. 



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



very small Okyzomvs, 548. 



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



PKROMYsrus, 549. 

 hhh. Tail closely haired, scarcely longer than head. 



OXYCIIOMYS, 550. 



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



or more. {Neotumime.) Nkotoma, 551. 



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

 tail long, scant-haired orfcaly (J/urinfc; old world species, introduced 

 in the United States) Mus. 



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



1039. F. zibethicus (L-). INIi'skuat. Color dark brown. 

 L. 22i. T. 11. E. N. Am. ; every wht-re. Largest of our Murida ; 

 buildni'.; houses or burrows about streams aud ponds. (Lat., 

 zibiAha, tbe Civet, from the odor.) 



1040. F. macroclon Merriam. Color very murh darker; 

 teeth vcrv much iaro;L'r, others like the couimon muskrat. Dismal 

 Swamp, Va. (fxaKpos, lar;^e; 68ovi, tooth.) 



543. SYNAPTOMYS Baird. (crvvdnro), to join; /iC?, mouse; 

 connecting lemmings and mice.) 



1040. S. cooperi (Baird). Lemmino Moise. ]\Iou?e-color, 

 grayish below; head very large wilh long whiskers; fur Foft and 

 long. L. 45. T. |. Minn, to Mass., S. to mts. of X. C, a remark- 

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

 (To William Cooper of Iloboken, X. J.) 



1041. S. fatuua Bangs. Similar to .S". cooprri, but with much 

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

 and N. IL (Lat., foolish.) 



1042. S. helaletes M€>rriam. Size of .S. cooperi, larger fore 



