326 DIDBLPHriDiE, 



wholly black in " D. cancrivora,'' and white, or parti-ooloured in 

 var. azarw, but in all exceedingly variable. Sides of neot often 

 yellowish or rufous, especially in old specimens, a coloration 

 apparently due to some form of unctuous secretion in this region. 

 Underside with but few longer hairs, its colour dirty white, but the 

 tips of the hairs often more or less black. Pouch large and well 

 developed. Mammse from 5 to 13 *, one single central, and from two 

 to six lateral ones. Arms and hands, legs and feet always darker 

 than the body, brown or black. Foot-pads 6 — 5, the pads very 

 large, rounded, little prominent, their surfaces coarsely striated ; the 

 two haUucal pads touching one another. Second, third, and fourth 

 toes subequal, fifth toe considerably shorter, barely reaching to the 

 end of the second phalanx of the fourth. Tail very long, distinctly 

 prehensile, its base covered, for from one to four inches, with hairs 

 like that on the body, the hairy part most extended in the variety 

 azarce, least in " D. virginiana ;" the remainder scaly, the scales large, 

 averaging from 6 to 8 to the centimetre ; practically naked, a few 

 fine hairs only between the scales ; proximal half black, distal half 

 white or yeUow. 



Skull very large and powerful, with strong and early developed 

 muscular ridges and crests; noticeable also for the enormous in- 

 crease of size which may take place in it after fuUy adult age is 

 reached (compare the measurements on p. 341). Nasals long, much 

 expanded behind. Supraorbital edges rounded, not beaded, but 

 with distinct conical postorbital processes, immediately above 

 which the prominent temporal crest commences. Brain-case smaJl 

 and narrow, a considerable interval occurring between the post- 

 orbital processes and the intertemporal constriction. Palate rather 

 imperfect behind, with two large and several small vacuities opposite 

 the molars ; its posterior edge much thickened. Posterior nares 

 contracted laterally, the opening nearly two thirds as high as broad. 



Teeth large and strong, but all, and especially the premolars, very 

 variable in their size. P.' about one third the size of p.^ ; p.* 

 slightly larger than p.' M." much broader than long, from two 

 thirds to three fourths the size of m.^ Lower p.^ about one fifth 

 the size of p.^, and almost or quite touching it; the latter decidedly 

 larger, and projecting from 2 to 3 miUim. higher than p.* 



a (in spirit). e' (in spirit), 



millim, milliiii. 



Head and body 470 460 



Tail 430 400 



Lower leg 105 104 



Hind foot 62 57 



Ear 41 40 



Skull, see p. 341. 



* Tliere are only five mammsa in the only adult female in spirit available to 

 me, but Dr. Coues records thirteen in his paper on " D. virginiana." 



