PROFESSOR OWEN ON THE SPECIES OF PHASCOLOMYS. 489 
a difference of proportion corresponding with the indication afforded by the glenoid 
cavity of the scapula; its antero-posterior or short diameter is greater, in comparison 
with its transverse or long diameter, in Phascolomys latifrons (ib. fig. 2, a), where it 
extends lower dewn and is narrower at its termination at the back of the humerus, than 
in Phase. platyrhinus (ib. fig. 4,a). The entire bone is stronger, broader in proportion 
to its length, in Phase. latifrons (ib. figs. 1 & 2). 
In both species the proximal tuberosities are well developed, but they are relatively 
more so in Phase. latifrons (figs. 1 & 2, b,c). In this species the ‘ ecto-tuberosity ’ 
extends its base over half the diameter of the fore part of the humerus (ib. fig. 1, 4) ; 
in Phase. platyrhinus over two fifths (ib. fig. 5, 6). 
The ento-tuberosity protrudes inward further in Phase. latifrons (ib. figs. 1 & 2, ¢) 
than in Phase. platyrhinus (ib. figs. 5 & 4, ¢). 
The ridge (d) for the insertion of the conjoined ‘ teres major’ and part of the ‘ triceps’ 
is shorter, thicker, more prominent, and better defined in Phase. latifrons ; it is situated 
chiefly on the thenal or fore part of the shaft, near the inner surface; but more of it is 
visible in the anconal view in Phasc. latifrons (fig. 2, d) than in Phasc. platyrhinus 
(fig. 4, d). 
The line of insertion (e, ¢) of the large and complex ‘ pectoralis’ extends from the 
lower and fore part of the ecto-tuberosity to that of the deltoid ridge (f'), nearly along 
the mid line of the fore part of the humerus; but it is to the inner side of that line in 
Phase. latifrons (fig. 1, ¢, e'), and to the outer side in Phasc. platyrhinus (fig. 3, e, @). 
The outer contour of the humerus curves almost parallel with the ‘ pectoral’ ridge to 
the projecting angle of the deltoid one (f') in Phase. latifrons (fig. 1). This angle is 
less prominent in Phase. platyrhinus (fig. 3, f), and the distance between it and the 
‘ predeltoid ridge’ (g) is less. 
The ‘supinator ridge’ (h, h’) is strongly developed in both species, and terminates 
above in a freely projecting, sometimes unciform process (h); below, it rapidly expands 
into the ectocondylar triangular surface (h'), giving attachment to the origin of the 
‘extensor digitorum’ muscle, The entocondylar process (2) is more produced and angular, 
and is largest in Phase. latifrons (ib. fig. 1). The bony bridge (4) extending from the 
fore part of the humeral shaft to that angle (7) is thicker in Phase. latifrons (fig. 1) than 
in Phasc. platyrhinus (fig. 3). The foramen which it defines is large and elliptic in both 
species, 
The radial division of the distal articular surface (7) is hemispheroid anteriorly (ib. 
fig. 1, 7), the convexity subsiding somewhat as it is produced backward; the ulnar divi- 
sion (m) is almost flat transversely, convex from before backward; the joint in this 
direction is narrowest at its middle, where the ulnar passes into the radial division 
(Pl. LXXIV. fig. 13). Both divisions are larger, especially the ulnar one, in Phase. 
latifrons (fig. 1, m) than in Phase. platyrhinus (fig. 8,m). ‘The shaft of the humerus is 
least thick between the deltoid and supinator crests; and a deep sulcus is continued from 
