186 Mr. 0. Thomas on a new 



Like Azara's, Mr. Perrens's specimen is young, having its 

 milk-premolars still in position ; and it is therefore to be 

 hoped that he will obtain further and adult examples of this 

 very beautiful little animal. 



As to the affinities of the species, a comparison of its skull 

 with those of other members of the group shows that it is 

 really more nearly related to M. elegans, the Chilian opossum, 

 than to M. incanus, as we should now call the Minas Geraes 

 species, agreeing closely with the former in size and general 

 form, and sharing with it the unique character of not 

 having the nasals expanded posteriorly. In fact the only 

 obvious distinction between the two skulls is the fact that 

 the supraorbital edges of M. griseus are sharply square, even 

 in the young specimen, and those of M. elegans are more or less 

 rounded, at least up to an age considerably greater than 

 that of the M. griseus now described. In external characters, 

 however, the two are of course widely distinct. 



Deomiciops, gen. uov. 



General proportions much as in Micoureus. Ears short, 

 hairy. Tail thick, incrassated at base, furry throughout 

 (except just below extreme tip) . Proportions of hind toes as 

 in Philander. 



Skull with a large rounded brain-case. Interorbital region 

 broad, without ridges or postorbital processes. Broadest 

 point of palate at front edge of ?L?. Bulla? very large, 

 perfect, the posterior, petrosal, portion inflated as much as the 

 anterior. Lower jaw with the anterior part of each ramus 

 splayed outwards, and with an unusually short symphysis. 



Teeth. — Incisors broad, spatulate ; — more separated from 

 its fellow of the opposite side than from —. Canines very 

 short, the upper one not reaching a line drawn from the tip 

 of Eii to that of —, and the lower one also scarcely higher 

 than the last premolar. Two anterior upper premolars sub- 

 equal, rather smaller than the posterior one ; below, each 

 premolar is slightly larger than the one in front of it. Molars 

 more rounded than in Micoureus, and recalling, both in form 

 and the curvature of their series, those of Philander. 



This genus differs from all other opossums by the short 

 furry ears, the thick and hairy tail, the perfect and doubly 

 inflated bullae, the shortened canines, and the peculiar form 

 and positions of the incisors. In other ways it presents some 

 points characteristic of Philander and some of Micoureus', and 

 it is to this latter that I suppose it must be considered most 



