9. PSEtJDocHiEirs. 167 



but apparently, judging only from dried skins, there is one occasion- 

 ally present placed on the upperside of the base of the tail *. 



SJcull. Nasals generally projecting nearly or quite as far forwards 

 as the premaxillse. Interorbital space flat or concave, its edges 

 ridged or rounded, often inflated. Squamosal portion of zygomata 

 inflated as usual. Palate variable, generally nearly perfect. Bulto 

 as a rule rather more inflated than in Trichosurus. Base of 

 masseteric fossa generally with a small opening into the inferior 

 dental canal. 



DentitioT, -—X ^-^ -BCorO^ p, 1 (or 0) p 1 .0.3 .4 -^ 1.2.3.4 _..g 



uentimn .— i. j-^j-^j , u. —5—, r. j»».o.3».4' ^- 1.2.3.4- ■'■'' 

 or 17+ (at most) 5 x 2 = 36 or 40. 



Upper teeth all fairly uniform in length, but i.' generally longer 

 in proportion to the others than in Petauroides. Premolars variable 

 in size and in their distances from each other ; p.^ in section, from 

 one third to three fourths the size of p.* Molars with crescentic 

 ridges as in Petauroides. Lower intermediate teeth generally very 

 small and sometimes altogether absent ; when three are present 

 they have the positions of i.^ p.\ and p.^ In Ps. albertisi and 

 archeri, owing to the shortness of the jaw, there is only a single 

 intermediate tooth (probably i.^), which is, however, larger in 

 proportion than usual. Lower p.' elongated, as high as the molars, 

 with several distinct cusps. 



Range. New Guinea, Australia, and Tasmania. 



This geniis, with its close ally Petauroides, by the complicated- 

 subselenodont character of its molars, stands somewhat apart from 

 most of the other Phalangers, and approaches Phaseolarctus, in 

 which a rather simpler form of the same modification is observable. 

 In young Cuscuses, however, a tendency towards the same structure 

 is also visible, but the crests on the molars soon wear ofi', and then 

 there appears but little difference between their molars and the 

 simple smoothly quadricuspid ones of Petaurus, Daetylopsila, and 

 their allies. 



The species of Pseudoehirus fall naturally into three groups, of 

 which Ps. peregrinus, albertisi, and canescens may respectively be 

 taken as typical. The members of the first group are restricted to 

 Australia and Tasmania, of the third to New Guinea, while the two 

 species of the second occur, the one in North Australia and tho 

 other in New Guinea. All the species except Ps. peregrinus seem to 

 have rather restricted ranges, and this fact has been taken advantage 

 of ill the following synopsis, since, partly owing to' the absence of 

 spirit-specimens, characters of more than specific value have not 

 been easily found. 



* The appearances indicative of a glandular structure are specially strongly 

 marked in Ps. archeri and albertisi. 



