578 PROFESSOR OWEN ON THE AFFINITIES OF THYLACOLEO. 
in wear and the slight one in size may indicate the present fossil to have come from an 
older and somewhat (sexually ?) larger Tliylacoleo. The apex of the anterior lobe has 
been worn off, and the lower hind lobe shows abrasion; but there is as little approach 
in relative size and conformation of crown in the present thylacolean m 1 to that tooth 
in the phytophagous Diprotodonts (Plate 41, figs. 3 and 4) as was indicated by the 
thylacolean subject which first came to my hands. 
The tooth, m 2 , as indicated by its socket in Plate 14 (1871), is of the same 
relative size, but with a more acuminate crown than is indicated by the conjectural 
outline there given. 
The maxillary and mandibular fossils here described and figured add the entire 
dentition of Tliylacoleo carnifex to the series of mammalian modifications of the 
dental system with which Comparative Anatomy is now enriched ; and they afford sure 
grounds for physiological deductions as to the nature and habits of the extinct 
Marsupial. 
Antibrachial bones of Tliylacoleo.—Of the bones and portions of bone referable by 
size to this genus and discovered in the same cave with the jaws and teeth last described 
are those of the fore-arm (Plate 40), of which the ulna (fig. 4) lacks only two inches of 
its distal end, according to the proportions of that bone in the larger Felines: this 
comparison is made from its being associated with an entire radius (ib., fig. 1) of the 
same length as that of the Lion : both fossils form part of the same limb of the leonine 
Marsupial. 
The articular surfaces in these fossils are as closely adapted to the divers movements 
of a fore-arm required for the application of the paw of a carnivore as in the Felines. 
The proximal end of the radius is occupied by an articular surface (ib., fig. 2) in two 
continuous portions, the larger and terminal one (fig. 3, a) being moderately concave 
for adaption to the radial condyle of the humerus, the smaller convex surface (ib., b), 
bending 1 down on the inner or ulnar border for articulation with the outer or radial 
concavity (fig. 5, b), continued from the larger and deeper trochlear surface (ib., a), near 
the humeral end of the ulna. 
The proximal or humeral cavity of the radius is not circular as in herbivorous 
Marsupials, hut is less oblong than in Leo; it is similarly continued upon a thick 
convex border, extended to form the surface b, fig. 3. 
The shaft of the radius describes the same slight curve “ radiad,” or on the outer side, 
and maintains the same nearly uniform breadth to the distal expansion, as in the Lion. 
The radial, or free, border is similarly obtuse ; the opposite border ( cl ) is for the most 
part roughly trenchant. The process (fig. 1, c) for implantation of the brachialis 
externus muscle holds the same relative position to the proximal end as in Leo. At 
the expanded distal end the elongate tuberosity (e) above the produced radial or outer 
angle for the carpal joint shows the same oblique groove for the tendon of the extensor 
carpi radialis. The tuberosity (f) answering to that giving insertion to the tendon of 
the supinator longus in the Lion, is nearer the ulnar angle of the distal expansion, 
