210 
PKOFESSOE OWEN ON THE FOSSIL MAMMALS OF ATJSTEALIA. 
part of the thigh-bone in Birds, is well shown in the femur of Macropus Titan (ib. 
fig. 2, w) as in that of Palorchestes (Plate 23. fig. 2, w ). 
The epiphyses are confluent with the shaft at both ends of the femur, but the line of 
separation is traceable in the fossil as in the figured femur of Macropus rufus above 
referred to. 
I may here refer to portions of fossil femora which depart from the type of the two 
already described by deviating further from the characters of the femur in the existing 
species of Macropus. The chief difference is in the smaller and shallower depression 
(y) above the outer condyle, such depression being filled up, as it were, by a rough and 
thick ascending process of the distal epiphyses, of which a rudiment only exists in the 
femur of Macropus Titan (Plate 27. fig. 4, z) and of Palorchestes Azael (Plate 23. 
fig. 2, z ). The femora with the larger and longer “ clamping” process are thicker in 
proportion to their length than in the above-cited fossils, and still more so than in the 
recent Kangaroos. This stronger type is manifested by full-sized or mature femora of 
three dimensions, of which the distal end of the largest is figured in Plate 23. fig. 3. I 
shall at the conclusion of the present “ Part ” adduce evidence which leads me to deem 
these fossils to belong to the genus Procoptodon ; and I, provisionally, refer the portion 
of femur figured and the shorter type of calcaneum in the same Plate (fig. 5) to Pro- 
coptodon Goliah. 
§ 10. Sthenurus Atlas (Restoration of the teeth and part of the skull). — Confirmation of 
the ascription of the second type of upper third incisor to an extinct species of Kangaroo 
with a large premolar tooth has been had by the reception of a specimen of that part 
of the skull and dental system which, as a rule, is wanting in cranial fossils of these 
extinct Marsupialia. 
This specimen consists of the facial part of the skull, from the anterior halves of the 
orbits to the ends of the premaxillaries, with their incisor teeth (Plate 25. fig. 2, 
Plate 26. fig. 4). 
The molar dentition is represented by an anterior tooth of trenchant character ( d 3), 
followed by three double-ridged molars on the left (Plate 25. d 4, m 1, m 2) and two on 
the right side (Plate 26. fig. 4, d 4, m 1 ). The third on the left ( m 2) is emerging from 
its socket with the ridged summits of the lobes narrow ; a portion of a formative cavity 
of a larger molar is preserved behind that tooth. This evidence of immaturity is 
supported by the incomplete exclusion of the crown of the third incisor (ib. ib. i 3) ; 
and the correspondence of the stage of dentition with the second (b) of the series in 
Macropus major , figured in my ‘Anatomy of Vertebrates’*, was demonstrated by the 
usual test, viz. the exposure of the crown of the replacing tooth (Plate 26. fig. 4, p 3) in 
its formative alveolus above the deciduous teeth (d 3, d 4) in place and use. The third 
bilophodont tooth ( m 2 ) on the left side is not so far advanced as its homologue in the 
jaw showing the third stage (op. cit. ib. c) of the dentition of Macropus major. 
The germ of the premolar and the crowns of the deciduous teeth in place (d 3, d 4, 
* 8vo, 1868, vol. iii. p. 380, fig. 296. 
