286 
the calcaneum; a greater part of the super- 
incumbent pressure is transmitted by a trans- 
versely extended convex anterior surface to the 
scaphoid and cuboid bones. This form of 
the astragalus is also characteristic of the Koala, 
Petaurists, Dasyures, and the Pedimanous 
Marsupials (d, fig.111). In the Kangaroos, 
Potoroos, and Perameles which have the pedes 
saltatorii, the fibular articular surface of the 
astragalus is bent down as usual at nearly right 
angles with the upper tibial surface. 
The calcaneum in the Wombat presents a 
ridge on the outer surface which serves to sus- 
tain the pressure of the external malleolus which 
is not articulated to the side of the astragalus. 
The internal surface which joins the astraga- 
lus. is continuous with the anterior slightly 
concave surface which articulates with the 
cuboides. The posterior part of the bone is 
compressed, it projects backwards for nearly 
an inch, and is slightly bent downwards and 
inwards. This part is relatively shorter in the 
Koala, Phalangers, Opossums, and Petaurists, 
but it is as strongly developed in the Dasyuri 
as in the Wombat. The anterior part of the 
calcaneum of the Phalangers is shown at e, 
Sig. 111. 
In the Dasyurus macrurus I observe a small 
sesamoid bone wedged in between the astragalus, 
tibia, and fibula at the back part of the ankle- 
joint. In the Petaurus taguanoides there is a 
supplemental tarsal bone wedged in between 
the naviculare and cuboides on the plantar sur- 
face. Inthe hand-like foot of the Phalanger 
the structure of the tarsus is shown in fig. 111: 
J is the naviculare, g the internal cuneiform, and 
h the os cuboides. In the Wombat the sca- 
phoid, cuboid, and three cuneiform bones have 
the ordinary uses and relative positions. 
The analogy of the carpal and tarsal bones 
is very clearly illustrated in this animal. The 
anchylosed naviculare and lunare of the hand 
correspond with the astragalus and navicu- 
lare of the foot, transferring the pressure of 
the facile majus upon the three innermost 
bones of the second series. The long, back- 
ward-projecting pisiform bone of the wrist 
closely resembles the posterior process of the 
os calcis; the articular portion or body of 
the os calcis corresponds with the cuneiforme 
of the carpus; the large carpal unciform re- 
presents the tarsal cuboides, and performs the 
same function, supporting the two outer digits ; 
the three cuneiform bones of the foot are obvi- 
ously analogous to the trapezium, trapezoides, 
and os magnum. The internal cuneiform bone 
is the largest of the three in the Wombat, al- 
though it supports the smallest of the toes. It 
is of course more developed in the Pedimanous 
Marsupials, where it supports a large and op- 
ble thumb. 
In the Wombat the metatarsals progressively 
increase in length and breadth from the inner- 
most to the fourth ; the fifth or outermost meta- 
tarsal is somewhat shorter but twice as thick, 
and it sends off a strong obtuse process from 
the outside of its proximal end. A correspond- 
ing process exists in the Phalangers (fig. 111). 
The innermost metatarsal of the Wombat (fig. 
MARSUPIALIA. 
105) supports only a single phalanx ; the rest 
are succeeded by three phalanges each, pro- 
gressively increasing in thickness to the outer- 
most; the ungueal phalanges are elongated, 
gently curved downwards, and gradually dimi- 
nish to a point. 
In the Myrmecobius the tibial or 
most toe is represented by a short rudim 
metatarsal bone concealed under the ski 
In the Dasyures the innermost toe has 
phalanges, but it is the most slender and does 
not exceed in length the metatarsal bone of th 
second toe. In the Petaurists it is rathe 
shorter than the other digits but is the strongest, 
and in Petaurus taguanoides the terminal 
phalanx is flattened and expanded ; the te 
set wide apart in this genus. In the Opossums 
and Phalangers the innermost metatarsal b 
is directed inwards apart from the rest, am 
together with the first phalanx is broad and flat. 
The second phalanx in the Opossums support 
a claw, but in the Phalangers is short, trans 
verse, unarmed, singularly expanded in 
Cookii, but almost obsolete in Ph. ursin 
(fig. 111,1). Inall the preceding genera there 
are two small staan 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 che 1 
istic of the Marsupial animals may be discerned 
in the Petaurists, in the slender condition of 
the second and third toes, as com ith 
the fourth and fifth. In the Phalangers t 
diminution of size of the second and third te 
counting from the hallux, is more marked, 
They are, also, both of the same length and 
have no individual motion, being united 
gether in the same sheath of integument as far 
as the ungueal phalanges, whence the name of — 
Phalangista applied to this genus (fig. 111, 
2 and 3). - 
In the saltatorial genera of Marsupials 
degradation of the corresponding toes is ex= 
treme, but though reduced to almost fila- 
mentary slenderness they retain the usual num= 
ber of phalanges, and the terminal one of each 
is armed with a claw. These claws being the 
only pe of the rudimental digits which pro- 
ject freely beyond the integument, they 
like little appendages at the inner side of the 
foot for the purpose of scratching the skin 
dressing the fur, to which offices they ar 
exclusively designed. The removal of the i 
nermost toe, corresponding with our g 
toe and the hallux of the Pedimana, commenc 
in the Perameles. In one species I find t 
metatarsal bone of this toe supports only 
single rudimental phalanx which reaches to the ~ 
end of the next metatarsal bone, and the inter- 
nal cuneiform bone is elongated. In another 
species the internal toe is as long as the abortive 
second and third toes, and has two phalanges, 
the last of which is divided by the longitudinal 
fissure characteristic of the ungueal phalanges — 
in this genus. In the Perameles lagotis the — 
innermost toe is represented by a rudi 
metatarsal bone, about one-third the length of 
the adjoining metatarsal. 
Ref 
me, 
hee inal 
La 
