11. POTOEOUS. 117 



" Thbugh these animals stand as much, on the hind legs as the 

 Bettongim, they run in an entirely different manner, using the fore 

 as well as the hind legs in a sort of gallop ; they also never attempt 

 to kick with their hind legs." 



The species are extremely similar externally, while in their cranial 

 characters they present such a considerable range of variation as to 

 make their proper discrimination by no means easy. 



Synopsis of the Species. 



I. External Chaeaotees. 



A. Naked part of rhinarium running back for 



some distance along the top of the muzzle. 



Head long and narrow. Hind foot, in 



adults, more than 65 millim, long. 

 a. Size generally larger. East Australian . . 1. P. tridactylus, p. 117. 

 6. Size smaller. West Australian 2. P. gilberti, p. 120. 



B. Naked part of rhinarium not running back 



along the top of the muzzle. Head short 

 and broad. Hind foot less than 65 millim. 

 long, 

 c. Size small. West Australian 3. P. platyops, p. 121. 



II. Ceanial Chabactees. 



A. Muzzle elongated. Orbit to anterior nares 



more than 28 mUlim., always nearly equal- 

 ling, generally more than, the zygomatic 

 breadth. 

 a. Muzzle scarcely inflated laterally, its upper 

 outline straight or eoncave. P.* 6 mil- 

 lim. or more 1. P. tndactylus, p. 117. 



6. Muzzle decidedly inflated laterally, its 

 upper outline convex. P.* less than or 

 barely 6 millim 2. P. gilberti, p. 120. 



B. Muzzle very short. Orbit to anterior nares 



26 millim. or less, not exceeding three 

 fourths of the zygomatic breadth. / 

 e. P.* very small, about 4-5 millim. long .... 3. P. platyops, p. 121.. 



1. Potorous tridactylus. 



Kanguroo Eat, Phillip, Voy. Botany Bay, p. 277, pi. xlvii. (animal) 



(1789). 

 Poto-roo, White, Joum. Voy. N. 8. W. p. 286, pi. Ix. (animal) (1790) ; 



Vicq-^Azyr, Syst. Anat. Quadr. {Encycl. MHh.) li. p. 645 (1792). 

 Didelphis tridactyla. Ken: Linn. An. K. p. 198 (1792) ; Turt. Idnn. 



S. N. i. p. 67 (1806). 

 Didelphis potpru, Meyer, Syst. Uebers. Zool. Entd. p. 13 (1793). 

 Yerboa potoru, Bechst. Syst. TJebers. Vierf. Thiere, ii. pp. 356 & 



686 (1800). 

 Didelphis murina, Cuv. Tabl. Elem. p. 126 (1798) {nee lAnn.) ; Besm. 



N. Diet. d'H. N. (1) xii. p. 358 (1803). 

 Macropus minor, Shaw, Gen. Zool. i. pt. 2, p. 513, pi. cxvi. (animal) 



