322 BlDELPHYIDiE. 



f^. Nasals not expanded behind. 

 /^ Supraorbitjul edges square. 

 Upper ins.i-3 about 5 or 5'5 



millim 13. H. ekgans, p. S51. 



B. Size small, basal length not exceeding 



about 40 millim. Lower p.* as large 



as or laj^er than p.* 



c. Nasals much expanded behind. Suprar 



orbital edges rounded. Temporal 



ridges touching, sometimes forming 



crests in old age V. Subgenus Fbeamys, p. 363. 



e'. Interorbital region narrow, parallel- 

 sided; postorbital processes and 

 temporal crests formed in adult life. 

 g'. Size large, basal length exceeding - 



32 millim. 

 g'. Teeth small. Upper ms.i-* 



about 5'2 millim 14, 2). dimidiata, p. 366. 



/'. Interorbital region smoothly rounded, 

 generally broad; no postorbital 

 processes at all, and temporal 

 crests only formed in extreme old 

 age. 

 V, Size large, basal length more than 

 31 millim. 

 W, Skull broad and strong ; teeth 

 large. Upper ms.i-8 more 

 than 5'5 mmim. 

 S'*. Upperms.i-35'8to6-5millim. 15. D. Jrmco«rfate, p. 366. 

 A*. Upper ms.i-3 6-2 to 7-7miUim. 16. B. domistica, p. 368. 

 »■'. Skull narrower ; teeth small, 



upper ms.i-3 about 4'6 millim. 17. D. sccdops, p. 369. 

 ^^ Size medium, basal length 26-81 

 millim. Ms.i-3 about 6 milUm. 

 _;■'. Interorbital breadth less than 



6 millim 18. D. hemeli, p. 360. 



k^, Interorbital breath 6 millim. 



or more 20. D. americana, p. 363. 



y. Size very small, baeal length less 

 than 26 millim. 

 P. Muzzle flattened, broad. Zy- 

 gomatic breadth more than 



12 millim 21. D. iheringi, p. 364. 



»i'. Muzzle rounded, narrow. 

 Zygomatic breadth less than 

 12 millim '. 19. Z>. sorex, p. 362. 



,>. (Oraaial ch^acters unknown) . . . . { g; g ZfXia',fim. 



I. Subgenus DIDELPHYS. 



Size large. Fifth hind toe markedly shorter than the second, 

 third, and fourth, which are subequal. Pouch present, well deve- 

 loped. Eur of two sorts, the ordinary short fur mixed with long 

 coarse bristles. 



Skull with a small narrow brain-case, its most constricted point 



