MACROPODIDA 163 
jaws always having large, simple, compressed crowns, with a nearly 
straight or slightly concave free cutting edge, both outer and inner 
surfaces usually marked by a series of parallel, vertical grooves and 
ridges, these teeth being either set in the same line with the 
molars, or slightly bent outwards. Molars with quadrate crowns, 
having a blunt, conical cusp at each corner, the fourth notably 
smaller than the third, sometimes rudimentary, and appearing early. 
Fore feet narrow; three middle toes considerably exceeding the 
first and fifth in length; their claws long, compressed, and but 
slightly curved. Hind feet as in Macropus. Tail long and hairy, 
sometimes partially prehensile, being used for carrying bundles of 
grass with which these animals build their nests. 
The Potoroos or Rat Kangaroos are all small animals, none of 
them exceeding a common rabbit in size. They inhabit Australia 
and Tasmania, are nocturnal, and feed on the leaves of various 
Fia. 54.—Skull and Teeth of Rat Kangaroo (Bettongia lesuewiri). vc, Upper canine. 
The other letters as in Fig. 51. 
kinds of grasses and other plants, as well as roots and bulbs, which 
they dig up with their fore paws. Nine species are known, present- 
ing a considerable range of diversity in minor characters, and 
admitting of being grouped in four principal sections, which may 
be allowed the rank of genera. These are: 
Potorous.\—Head long and slender. Auditory bulls some- 
what inflated. Ridges on premolars few and_ perpendicular. 
Large palatine foramina. Tarsus short. Muffle naked. Three 
species, viz. P. triductylus, P. gilberti, and P. platyops ; the last two 
being confined to West Australia. 
Bettongia.2—Head comparatively short and broad. Ears short 
and rounded. Auditory bulle generally much inflated. Large 
palatine foramina. Tarsus long. Ridges on premolars numerous 
1 Desmarest, Nouv. Dict. d’Hist. Nat. ser. 1, vol. xxiv. Table Meth. ». 20 
(1804). Syn. Hypsiprymnus, Miger, Prodromus Syst. Mam. p. 79 (1811). 
* Gray, Charlesworth’s Mag. Nat. Hist. vol. i, p. 584 (1837). 
