326 PROF. E. COLLETT ON MAMMALS [Mar. 16, 



are very conspicuous, and give the orange-rufous back a grizzled 

 silvery appearance. 



The terminal pencil of tlie tail is rather variable in colour, in 

 some specimens being almost brownish black. 



Skull. Perhaps none of the specimens are perfectly adult, as the 

 last molar has in no case reached its full growth. Length of the 

 largest specimen (a male) 78 mm., breadth 44'5 mm. 



li iterorbital space in larger specimens slightly concave ; the 

 fronto-nasal suture strongly concave or forming an obtuse angle 

 (open in front). 



Posterior palatal foramina large, reaching from front or middle 

 of m- to middle of m'K The bony bridge behind the foramina very 

 thin, with many small openings. 



Teeth. The dentition of this species is rather peculiar, and the 

 skulls in the collection seem as if they had five molars and no 

 premolar. Tlie anterior of the teeth is, however, the milk p*, 

 which has exactly the shape of a true molar. 



The eight skulls represent three different stages. 



Young stage. In two young specimens (length of skull 49 mm. 

 and 59 mm.) both premolars {ix" and the milk p*) are present. 

 P' has a normal shape, not very different from that in other 

 species ; it has four cusps (the anterior indistinctly divided in two), 

 with shallow notches between them. Its length equals that of p*. 



Middle stage. One skull, length 73 mm., breadth 42 mm. P^ is 

 still present in the right side of the upper jaw, but has fallen out 

 on the other side, and below. Consequently this tooth seems to 

 be changed at the time when m^ is appealing. 



Nearlg adidt stage. Pive skulls, length 72 mm. to 78 mm. As 

 stated above, m'' has not reached its full development in any of 

 these, although one of them belongs to the mother of one of the 

 young ones. 



The perfectly molar-like jj'* is present in all ; most likely it is 

 changed at a very late period, and it may even be an open 

 question whether it is ever changed at all. 



Hah. Common on the granite on the western heads of the river 

 Mary. On Daly Eiver it was met with in one locality onh' 

 (about a hundred miles from the river mouth). 



Native name : Bolwak. 



19. Peteogalh beachyotis, Gould, 1840. 



Petrogale brachyotis, Thos. Cat. Mars. Monotr. Brit. Mus. p. 69 

 (188S) ; Ogilby, Cat. Austral. Mamm. p. 49 (1892). 



N.Australia: Daly Eiver, July 20th- 21st, 1894 (three speci- 

 mens and one young in spirit). S. AUigator Eiver, April 14th, 

 1895 (one specimen). Mary Eiver, May llth-14th, 1895 (two 

 specimens and oue embryo). Union Town, Aug. 16tli, 1895 (one 

 specimen). 



Shin. There are seven specimens, besides one young from the 

 pouch and one embryo. 



To the detailed description of Mr. Thomas I may add that in 

 all the specimens there is a faint dark line down the centre of the 



