OF THE MARSUPIALIA. 401 
hooked process above the groove of the radial nerve. In all these, and especially in 
the Wombat, the deltoid process of the humerus is strongly developed : it is continued 
from the external tuberosity down the upper half of the humerus ; except in the Petau- 
rists, where, from the greater relative length of the humerus, it is limited to the upper 
third. The interspace of the condyles is occasionally perforated, as in the Perameles 
lagotis and Wombat. The articular surfaces at both extremities of the humerus have the 
usual form ; but it may be observed, that in some Marsupials, as the Koala, at the distal 
articulation the external convexity for the radius has a greater relative extent than 
usual, and the ulnar concavity is less deep. 
The bones of the fore-arm present little to detain our notice. They are always distinct 
and well developed, and their adaptation to pronation and supination is complete. The 
prehensile faculty and unguiculate structure of the anterior extremities appear to have 
been indispensable to animals where various manipulations were required in the 
economy of the marsupial pouch. When, therefore, such an animal is destined, like 
the Ruminant, to range the wilderness in quest of pasturage, the requisite powers of 
the anterior members are retained and secured to it by an enormous development of 
the hinder extremities, to which the function of locomotion is restricted. 
We find, therefore, that the bones of the fore-arm of the Kangaroo differ little from 
those of the burrowing Wombat, the climbing Koala, or the carnivorous Dasyure, save 
in relative size. They present the greatest proportional strength in the Wombat, 
and the greatest proportional length and slenderness in the Petaurists, or Flying Opos- 
sums, in which the radius and ulna are in close contact through a great portion of their 
extent, and thus lend a firmer support to the outstretched dermal parachute. They are 
also long and slender in the Koala. In general the radius and ulna run nearly parallel, 
and the inter-osseous space is very trifling ; it is widest in the Potoroos. The olecranon 
is well developed in all the Marsupials. In the Pet. Taguanoides it is expanded, and 
truncate at the upper extremity; in the Virginian Opossum and Petaurists we find it 
more bent forwards upon the rest of the ulna, than in the other Marsupials. In the 
Wombat, where the acromion is the strongest, and rises an inch and a half above the 
articular cavity of the ulna, it is extended in the axis of the bone. The distal end of 
the radius in this animal is articulated to a broad bone representing the os scaphoides 
and os lunure. The ulna, which in the same animal converges towards a point at its 
distal end, has that point received in a depression formed by the cuneiform and pisiform 
bones ; these are bound together by strong ligaments, and the pisiform then extends 
downwards and backwards for two-thirds of an inch. The second row of the carpus 
consists of five bones. The trapezium supports the inner digit, and has a small sesamoid 
bone articulated to its radial surface. The trapezoides is articulated to the index digit, 
and is wedged between the scapho-lunar bone and os magnum; this forms an oblique 
articular surface for the middle digit. But the largest of the second series of carpal 
bones is the cuneiform, which sends downwards an obtuse rounded process, and receives 
3G2 
