OF THE MARSUPIALIA. 407 
more developed in the Pedimanous Marsupials, where it supports a large and opposable 
thumb. In the Wombat the metatarsals progressively increase in length and breadth 
from the innermost to the fourth ; the fifth or outermost metatarsal is somewhat shorter, 
but twice as thick, and it sends off a strong obtuse process from the outside of its prox- 
imal end. The innermost metatarsal supports only a single phalanx ; the rest are suc- 
ceeded by three phalanges each, progressively increasing in thickness to the outermost ; 
the unguial phalanges are elongated, gently curved downwards, and gradually diminish 
to a point. 
In the Myrmecobius the tibial or innermost toe is represented by a short, rudimental, 
metatarsal bone, concealed under the skin. 
In the Dasyures the innermost toe has two phalanges, but it is the most slender, and 
does not exceed in length the metatarsal bone of the second toe. In the Petaurists it 
is rather shorter than the other digits, but is the strongest ; and in Petaurus Taguanoides 
the terminal phalanges are singularly flattened and expanded; the toes are set wide 
apart in this genus. In the Opossums and Phalangers the innermost metatarsal bone is 
directed inwards, apart from the rest, and, together with the first phalanx, is broad and 
flat. The second phalanx in the Opossum supports a claw, but in the Phalangers is 
short, transverse, unarmed, and almost obsolete. 
In all the preceding genera there are two small sesamoid bones on the under side of 
the joints of the toes, both in the fore and hind feet. 
The commencement of a degeneration of the foot, which is peculiar to, and highly 
characteristic of, the marsupial animals, may be discerned, in the Petaurists, in the 
slender condition of the second and third toes, as compared with the first, fourth, and 
fifth. In the Phalangers this diminution of size of the second and third toes, counting 
from the hallux, is more marked ; they are also both of the same length, and have no 
individual motion, being united together in the same sheath of integument as far as 
the unguial phalanges, whence the name of Phalangista applied to this genus. In the 
saltatorial genera of Marsupialia the degradation of the corresponding toes is extreme ; 
but though reduced to aimost filamentary slenderness, they retain the usual number of 
phalanges, the terminal ones being armed with claws, which appear as appendages at 
the inner side of the foot, for the purpose of scratching the skin and dressing the fur. 
The removal of the innermost toe, corresponding with our great toe, and the hallux of 
the Pedimana, commences in the Perameles. In one species I find the metatarsal bone 
of this toe supports only a single rudimental phalanx, which reaches to the end of the 
next metatarsal bone, and the internal cuneiform bone is elongated. In another spe- 
cies the internal toe is as long as the abortive second and third toes, and has two pha- 
langes, the last of which is divided by the longitudinal fissure characteristic of the 
unguial phalanges in this genus. In the Perameles lagotis the innermost toe is repre- 
sented by a rudimental metatarsal bone, about one-third the length of the adjoining 
metatarsal. In the Poephagous Marsupials no rudiment of the innermost toe exists. The 
VOL. I1.—PART V. 3H 
