PROFESSOR OWEN ON THE AFFINITIES OF THTLACOLEO. 
579 
instead of rising midway between the terminal angles : and here I may remark that 
the Felines agree with the Marsupials in the presence of this muscle. In all minor 
modifications the leonine characters are closely repeated in the present fossil radius. 
The same general correspondence of structure prevails in the ulna (fig. 4). The 
olecranon (c) offers the same development, with tuberous and ridged indications for 
adequate implantation of the powerful extensors of the fore-arm : it is relatively 
longer, but with rather less breadth than in Leo. The proximal articular surface has 
the same trochlear character (a) and passes uninterruptedly, but with a similar defining 
line, into the concave surface (fig. 5, b) for the corresponding side of the head of the 
radius. The adaption of these joints for free pronation and supination, as well as 
flexion and extension of the fore-paw, is as strongly marked in Thylacoleo as in 
the similarly-sized placental Felines. The few noticeable modifications indicate the 
derivative relation to the inplacental group. 
In the existing Diprotodont Marsupials, whether climbers, flyers, burrowers or leapers, 
the bones of the fore-arm are freely articulated for both rotatory and flexile move¬ 
ments, a power which has been suggested to relate to manipulations of the nursing 
pouch; therefore, to be needed by the Kangaroo group as well as the rest. But in 
none, save the Wombat, does the proportion of the olecranon come near to that in 
Thylacoleo. The modifications of the radius and ulna for burrowing actions present 
differences, in number and kind, from those in Thylacoleo which need only a glance at 
the skeleton of Phascolomys to be appreciated. 
In other Diprotodonts, especially the species Macropus major, for example, nearest 
in size to Thylacoleo, the olecranon is not continued beyond the trochlear cavity to the 
extent of that joint longitudinally : the shaft of the ulna is relatively longer and much 
more slender. The radius, with a circular proximal end, gives a smaller and less 
definite lateral articular surface to a concomitantly smaller external (‘radial j offset 
from the trochlear articulation: the shaft of the radius is also relatively longer and 
more slender, and is proportionally less expanded at the distal end than in Thylacoleo. 
Claw-phalanx of Thylacoleo.—Passing over evidences of carpal and metacarpal 
fossils, my remarks will, here, be limited to the characters of the terminal or ungual 
phalanges. 
Fossil claw-bones are not few from the Thylacolean cavern, and these in shape and 
structure add instructive evidence of the nature of the quadruped to which, by their 
size, they may be attributed. By these characters a phalanx of a fore-paw may be 
selected: the talon which such bone supported and wielded was fully as large as that 
of the Lion, and indicates that it was sub-compressed, decurved and pointed. 
The basal articular surface (fig. 7, a) shows a pair of vertical concavities divided by 
a mid-ridge : it occupies the breadth and greater part of the height of the base, leaving 
about an equal but small extent of non-articular tuberous insertional portion above 
and below the trochle?ir joint. 
But the most instructive part of the phalanx is the extension from the upper and 
