﻿THE RAT-KANGAROOS. 65 



Characters. — Size medium ; naked portion of nose extending 

 backwards along the top of the muzzle ; face long and narrow; 

 hind feet long, short-haired. Fur and general coloration as 

 in last species ; tail grey at base, deepening to black at tip. 

 Length of head and body about 15 J inches ; of tail 7 inches. 



Distribution. — South-western Australia. 



III. COMMON RAT-KANGAROO. POTOROUS TRIDACTYLUS. 



Didelphis tridactyla^ Kerr, Linn. Anim. Kingdom, p. 198 



(1792.) 

 Didelphis murina, Cuvier, Table Element., p. 126 (1798). 

 Hypsiprymnus murinus, Goldfuss, Handb. Zool., p. 447 



(1820). 

 Hypsiprymnus apicalis, Gould, Mamm. Austral., pi. Ixviii. 



(1851). 



Potorous rufus, Higgins and Petterd, Proc. Roy. Soc, Tas- 

 mania, 1883, p. 181. 



Potorous tridactylus, Thomas, Cat. Marsup. Brit. Mus., p. 1 1 7 

 (1888). 



{Plate VI I I.) 



Characters. — Size variable, large or medium ; other external 

 characters as in P. giiderti, but the naked portion of the nose 

 extending rather further upwards on the muzzle. Length of 

 head and body reaching to 16^ inches ; of tail 9 inches. 



Distribution. — New South Wales, Victoria, South Australia, 

 and Tasmania. 



Varieties. — One Tasmanian race {P. apicalis) attains larger 

 dimensions than specimens from the mainland, and also has 

 the fourth premolar tooth larger and with four instead of three 

 grooves. There is also a dwarf Tasmanian form {P. rufus) in- 

 ferior in size to mainland examples ; but intermediate varieties 

 appear to connect all three together. 



3 F 



