162 MARSUPIALIA 
molar (m 1), as to be most naturally mistaken for, or compared with, 
them in specific descriptions. . . . The necessary knowledge as to 
the stage of dentition in which any skull may he, can often be 
gained only by cutting open the bone either above and behind the 
first tooth of the series to see if the true permanent p 4 be still 
buried there (in which case, of course, that first tooth is only p 3), 
or behind the last visible molar to see if there be yet another tooth 
behind it, showing it to be m3 and not m4. The first plan is, 
as a rule, the better, since » 4 is generally by far the most 
important tooth for diagnostic purposes, and its characters have, 
therefore, in any case to be taken into account.” 
The Macropodide are divided into three well-marked sections : 
(1) the true Kangaroos (Macropodine) ; (2) a group consisting of 
smaller animals, commonly called Rat Kangaroos, or (improperly) 
“ Kangaroo Rats,” or sometimes Potoroos; and (3) the Hypsiprym- 
nodontince, now represented only by a single species. 
Subfamily Hypsiprymnodontinz.—Size very small. Claws 
small, feeble, and subequal. Hind feet with an opposable hallux. 
Tail naked and scaly. The fourth premolar twisted obliquely out- 
wards, as in Phalanger. Other teeth as in the Potorvine. 
This subfamily is now represented only by the genus Hyps?- 
prymnodon, which is a form of great interest, as showing a structure 
of foot connecting that of the Kangaroos with that of the Phalan- 
gers. The single known species, H. moschatus, was described by 
Ramsay from specimens discovered in north-east Australia. It 
was described almost simultaneously by Owen under the name of 
Pleopus nudicaudatus. From the resemblance in the structure of the 
foot and the obliquity of the premolars to the Phalangers Mr. 
Thomas has some hesitation as to which family should receive this 
genus, but the macropine characters of the mandible preponderate 
in favour of the Macropodide. 
Trichis2—A lower jaw of a much larger form from the Pleisto- 
cene deposits of Australia apparently indicates another member of 
this subfamily, having the outwardly directed and grooved pre- 
molar characteristic of Hypsiprymnodon. It differs, however, from 
that genus, and also from all other known Macropodide, in having 
a small tooth between the incisor and fourth premolar, which 
apparently represents a canine, or perhaps an anterior premolar. 
This form indicates, therefore, a closer connexion between the 
Phalangeride and Macropodide than any other. 
Subfamily Potoroinz.—The second section or subfamily, the 
Potoroine, have the first upper incisor narrow, curved, and much 
exceeding the others in length (Fig. 54). Upper canines always 
persistent, flattened, blunt, and slightly curved. Premolars of both 
1 Ramsay, Proc, Linn, Soc, N.S. Wales, vol. i. p. 33 (1876). 
* De Vis, Proc. Roy. Soc. Queensland, sev. 2, vol. iii, p. 8 (1888). 
