Mr, O. Thomas on Micoureus orriseus. 185 



o* 



Size rather less than in M. miirmus. Fur very short, 

 soft, and fine. General colour of the back soft mouse-j^rey, 

 almost exactly similar to ordinary specimens of Jilus mus- 

 culus, a resemblance by which Azara was also struck. 

 Instead of this colour, however, fading off gradually towards 

 the flanks and there meeting the white of the belly, as in 

 most species, it is sharply defined and separated from the 

 white underside by a broad band of paler grey, which gives 

 the species a quite unique appearance. The darker grey 

 commences between the eyes, broadens out to cover the crown 

 and back of neck, reaches its greatest breadth (about 

 20 millira.) in the centre of the back, and narrows again 

 sharply and decidedly as it reaches the tail. The eyes are 

 clearly ringed with black, as stated by Azara, while the 

 continuance forward on to the frontal region of the pale grey 

 lateral band causes the appearance of pale outer orbital rings, 

 separated in the middle line by the darker median colour, an 

 appearance which, admirably described by Azara, has caused 

 much trouble and confusion to workers who have tried to fit 

 his description on to other species. Ears large and leafy, 

 uniformly grey ; their anterior basal prominence little deve- 

 loped. Under surface from chin to anus pure sharply defined 

 white. Shoulders slightly darker than the lateral pale band ; 

 front of forearm paler grey, upper surface of hands white. 

 Hind limbs similarly coloured, the lower legs grey, the feet 

 white. Tail long, naked except for its basal quarter inch ; 

 grey above for three fourths its length, the terminal fourth 

 and the whole of the under surface white. 



Dimensions (approximate) of the skin of a young specimen 

 with p.^ still in place : — 



Head and body (apparently stretched) lOo millim. ; 

 tail 122; hind foot 14.' 



Skull : basal length (c.) 24 ; greatest breadth 14 ; inter- 

 orbital breadth 4"1 ; nasals, length 10, greatest breadth 2'2 ; 

 palate, length 13 ; combined lengths of "^liz? 4*9. 



The rediscovery of this pretty little opossum, of which, so 

 far as I know, no naturalist has seen a specimen since Azara 

 described it a century ago, is a matter of considerable interest, 

 as it clears up a question which has puzzled many writers on 

 the subject. The correspondence of Mr. Perrens's specimen 

 with Azara's description is really reraarkablv close, as the 

 dimensions agree exactly, the 2Ius viusculus-\ike colour and 

 texture of fur are present, and the puzzling outer pale rings 

 round the eyes referred to by him are here produced by the 

 division of the pale facial colour by the anterior extremity of 

 the darker dorsal area. 



