Dr. J. E. Gray on species of Mammalia from the Aru Islands. 221 



third and fourth on the right side of the jaw, is a cavity which 

 appears to have been filled with a tooth like the third one, but 

 there is no appearance of the tooth or cavity on the other side. 

 Canines? n, upper small, compressed, conical, tapering like, but 

 smaller than, what I have called the hinder cutting teeth (fig. 3). 

 Grinders j-^J small, in two nearly straight lines parallel to each 

 other, and the hinder ones in each jaw rather smaller than the 

 front ones ; the front upper small, triangular ; the others four- sided 

 and square, with four tubercles, the outer front tubercle of the 

 second tooth being rather larger than the rest, which are nearly 

 equal among themselves, and the front lower grinder has only one 

 larger tubercle in the place of the two in the others (figs. 4, 5). 



Fijr. 3. 



Fig. 5. 



This genus is very distinct from the other genera of Phalangistina, 

 in the elongated and depressed form of the tail, the formation of the 

 fore-feet, and especially in the disposition and form of the teeth, as 

 well as in the broad depressed skull. 



The following observations may assist in showing the value of 

 these characters. 



In Cuscus the fingers are rather longer than in Hepoona, and the 

 third or middle finger is the longest, the others becoming gradually 

 shorter on each side. 



In Phalangista proper (that is Trichosurus of Mr. Waterhouse) the 

 fingers are moderately long, the second and third are the longest and 

 equal, the fourth longer than the first, and the fifth or inner one 

 the shortest. 



The hand of the Hepoona is very like that of Phalangista, both in 

 the proportion and form of the fingers ; but the two inner fingers are 

 rather separated and opposable to the other three. 



The tail, though covered with hair, is very unlike those of the 

 genera Hepoona and Phalangista, and is more like that of a squirrel, 

 but not so bushy ; in Hepoona it is tapering and covered with 

 shortish hair, and has a slender tip ; in the more perfect specimen 



