490 PROFESSOR OWEN ON THE SPECIES OF PHASCOLOMYS, 
the interval obliquely downward and inward, expanding and becoming lost upon the fore 
part of the broad distal end of the bone. 
At the back or anconal part (ib. figs. 2, 4) the head of the ieee (a) is seen to 
descend lower and in a more angular form in Phase. latifrons (fig. 2, a) than in Phase. 
platyrhinus (fig. 4, a). The short transverse ridge for the humeral head of the triceps 
is most strongly marked in Phasc. latifrons (fig. 2, ). The margin of the supinator 
ridge is thicker, and is bent forward in the bare-nosed species (fig. 4, /). 
The bone is reduced to transparent thinness between the coronal (0) and anconal (p) 
depressions; but I have not noticed a vacuity here in either of the continental species, 
as in one individual of the Tasmanian Wombat’. 
The figures 1-4 of Pl. LX-XII. will supply other features of the bone, not noted in 
the text, which has been purposely restricted to the salient differential characters of the 
humerus in the two continental species of Phascolomys, most likely to be available in 
the determination of fossils. 
- The radius of Phascolomys latifrons (P|. LX XII. figs. 5-8) is a strong bone, slightly 
bent, with the convexity forward; the head (fig. 7) is subcircular and concave for 
adaptation to the humeral ball (ib. fig. 1,2). From the outer side of the head a narrow 
semielliptical convex surface (‘lesser sigmoid cavity’ of Anthropotomy) (figs. 5 & 6, a) 
is adapted to the radial concavity of the ulna (fig. 11, ¢). A few lines below the neck 
of the radius projects a large tuberosity (figs. 5 & 6, 4) for the biceps. 
The shaft gradually expands as it descends, and assumes a triedral shape; a ridge 
(fig. 5, c) for the insertional fascia of the ‘ supinator longus’ defines at the lower third 
of the shaft the fore from the inner surface of that part of the bone. This ridge leads 
to a small tuberosity (d) above the base of the short thick styloid process (¢). The 
interosseal ridge or angle is well marked, and shows a rough tract at its middle third 
(fig. 6, f). The broad distal articular surface (fig. 8) is gently convex from before 
backward, concave from side to side; it is adapted to the large scapho-lunar carpal 
bone, and to the radial facet of the cuneiform. 
The head of the radius is less circular in Phascolomys platyrhinus than in Phase. 
latifrons, and the bicipital tubercle is rather nearer to it; the entire bone is less thick 
in proportion to its length; but the differences are not such as to call for a drawing of 
the bone in this species. 
The ulna (Plate LXXII. figs. 9-11) in both Wombats is remarkable for the length and 
breadth of the olecranon (a, a’), and for the concavity (4) continued from its ulnar (inner) 
side (figs. 9, 10) downward below the proximal articulation. This presents three con- 
tinuous facets—one (fig. 11, ¢) for the ulnar division (fig. 1, m) of the humeral articu- 
lation, one (fig. 11, d) for the back part of the radial division of the same (fig. 2, 2), 
and the third (fig. 11, e) for the side of the head of the radius (fig. 5, @). 
The thick hind border of the olecranon contracts into the sharper hind border of the 
1 «On the Osteology of the Marsupialia,” tom. cit. p. 401. 
