DIDELPHT8. 



345 



/. Nat. viii. p. 369 (1842) ; Schim, Syn. Mamm. i. pp. 504 & 605 



(1844) ; Wagn. Abh. Ak. Munch, v. pp. 146 & 147 (1847) ; id. 



Schr. Siiug. Supp. v. pp. 242 & 24-3 (1855) ; Natt. Pelz. Bras. 



Sdug., Verh. z.-b. Wien, xxxiii. Anh. p. 114 (1883). 

 Micoureus murinus and dorsigerus, Less. N. Tail. JR. A., Mamm. 



p. 186 (1842) ; Gerv. H. N. Mamm. ii. p. 287 (1865). 

 Philander murinus and dorsigerus, Gray, List Mamm, B. M. p. 101 



(1843); Gerrard, Cat. Bones Mamm. B. M. p. 140 (1862). 

 Didelphys impavida, Tschudi, Favn. Peruana, p. 149, pi. ix. (animal) 



(1844) ; Wagn. Schr. Siiug. Supp. v. p. 240 (1865) ; Gieb. Sdug. 



p. 714 (1859). 

 Didelphys musculus, Cahanis, Schomb. Brit. Guiana, iii. p. 778 



(1,848) ; Wagn. Schr. Siiug. Supp. v. p. 245 (1865). 

 Didelphys (Grymseomys) murina, Burm. T/tiere Bras. i. p. 188 



(1854). 

 GrvmsBomys murinus, dorsiger, and impavidus, Burm. BrlUut. Faun. 



Brds. pp. 80 & 81 (1856). 



MXTEINE OpOSStJM. 



Size markedly smaller than iu D. dnerea ; form slender and 

 delicate. Fur thick and close, straight, not woolly. General 

 colour deep dull rufous, exact tone very variable. Rhinarium with 

 two notches on each side below. Face greyer and paler than the 

 back, the dark stripes through the eyes generally very conspicuous, 

 and contrasting markedly with the paler colour between them. 

 Ears (PI. XXVI. fig. 9) much as in B. dnerea ; laid forward (in 

 spirit-specimens) they reach beyond the anterior canthus of the eye; 

 their internal basal projection very long and prominent. Back deep 

 gre3'ish rufous, sides brighter and clearer. Chin white ; chest and 

 belly yellowish white, the hairs generally grey-based laterally, and 

 pure white down the median line, lines of demarcation quite 

 vague and undefined. Outsides of limbs like back, inner sides white. 

 Pouch absent ; mammse, one ventral and from 4 io 7 lateral, total 

 9 to 15*. Hands and feet white or pale grey. Pads as in B. dnerea. 

 Tail long, slender, cylindrical, furry for barely half an inch at its 

 base ; the remainder with only a few fine scattered hairs upon it ; 

 its colour grey, sometimes gradually lightening terminally. 



Skull and teeth in all respects similar to those of B. dnerea, but 

 very materially smaller (see dimensions, p. 351). Correlated with 

 this reduction in size there is also a marked reduction in the 

 development of the supraorbital ledges, which are, however, always 

 present, even in immature specimens, being present at the least in 

 the form of a narrow but distinct beading along the supraorbital 

 margins. 



* I am as yet unable to make out what degree of local constancy obtains in 

 the number of the mammse. In the present series, specimens o and p, from the 

 Island of Grenada, both have 7-1-7=15 mamma ; specimens e~g, from Central 

 America, 6-1-6=13; and all the rest. South American, either 5-1-5=11, or 

 4-1-4=9. No other differences of any kind can be found between the speci- 

 mens from these various localities. It is unfortunate that the number of 

 mammsB in the Mexican and Tres Marias specimens cannot be determined. 



