DIDELPHTIDiE. 



315 



Slcull Measurements of Myrmeoobius. 



Family VI. DlDELPHYIDa:. 



Polyprotodont Marsupials adapted for an arboreal, predatory, 

 omnivorous, or insectivorous life. Metatragus variable in size. 

 Limbs subequal ; fore and hind feet each with five toes, the latter 

 not syndactylous, but with a very large and widely opposable nail- 

 less hallux. Tail generally very long, naked, scaly, prehensile, 

 sometimes short, and more' or less hairy. Stomach simple. Csecum 

 small or moderate. Pouch generally absent, sometimes merely 

 composed of two lateral folds of skin separate at each end ; rarely 

 completff. 



Dentition : — I. 



1.2.8.4.5 



C.i,P.,_ 



M. 



x2=50. 



1.2.3.4 ''I'-^'l. 0.3. 4' -1.2.3.4 



Teeth rooted, sharp, cutting, carnivorous. Upper incisors small 

 and conical, the first larger than and separated from the others. 

 Upper premolars generally increasing in size backwards, and with, 

 as a rule, a marked diastema between p.' and p.° Lower premolars 

 well developed, their relative sizes variable. Molars multicuspid ; 

 with only three cusps visible externally. 



Tooth-change always present, the milk-premolar large and long- 

 persistent. 



Range. North and South America, from the United States to La 

 Plata. Also found fossil in Europe; 



This family is an exceedingly homogeneous one, its members pre- 

 senting a very small range of differentiation. It is, on the whole, 

 very closely allied to the Dasyuridce, from which, were it not for 

 its isolated geographical position, it would be very doubtfully 

 separable. 



