60 PROFESSOR OWEN ON THE 
The inner or under surface of the ilium is thickened into a kind of buttress (ib. fig. 1, e), 
terminating behind the ischiadic foramen. The breadth of the iliac bones and inter- 
vening sacrals, 1 inch behind the acetabulum, is 5 inches; at the back part of the 
pelvis it is 4 inches. The outer border of the posterior part of the ilium (ib. fig. 2, g) 
projects as an obtuse ridge above the ischiadic foramen and the succeeding expanded 
and confluent part of the ischium (ib. 63), which is vertically concave externally: the 
ilium, ischium, and pubis (ib. fig. 1, 64) have completely coalesced around the aceta- 
bulum. The pubis, which in this part is 7 lines thick, contracts as it becomes free 
to a diameter of 4 lines; it is smooth and convex below, and has been broken off near 
the acetabulum on both sides; the fracture shows its pneumatic structure. The ischium, 
as it recedes from the acetabulum, contracts to a trihedral column, with a vertical dia- 
meter of 4 lines; it is concave outwardly, convex inwardly, and suddenly expands 
below, about an inch from the acetabulum, to form part of the posterior boundary of the 
obturator foramen (ib. fig. 1, f), which is 9 lines in length, and is situated one half in 
advance of, and the other half beneath, the ischiadic foramen (ib. m). This latter 
is oval, with the large end forwards, 1 inch 3 lines by 10 lines in its principal dia- 
meters. Behind this foramen the ischium is confluent with the ilum for an extent of 
2 inches, or perhaps rather more, as the posterior margin of the pelvis is not entire in 
any of my specimens. The inner surface of the ischium forms a low, obtuse longitu- 
dinal ridge towards the pelvic cavity, losing thickness as it recedes from the acetabulum. 
The chief pneumatic foramina in the pelvis are on the inner surface, above the aceta- 
bulum, behind the trochanterian articulation, and behind the iliac confluence of the last 
sacral pleurapophyses,—also at the hinder part of the ilium, on each side of the transverse 
buttress (ib. @) near its posterior junction with the ischium. ‘The prerenal fossa (be- 
tween pl 4 & pl 8, fig. 1) is deep and subdivided by the diapophysial plates: the post- 
renal fossa is wide and shallow. 
§ 5. Sternwm. 
Of this instructive and determinative bone there are two specimens, the one most 
entire (Pls. XV., XVI. fig. 4 4, & XVIII.) measuring in a straight line, from the costal 
process to the hind border, 7 inches. The extreme breadth between the lateral pro- 
cesses (Pl. XVI. h) is 4} inches; from this diameter the bone contracts anteriorly to a 
breadth of 35 inches at the costal processes (ib. d), and posteriorly it contracts more 
rapidly to an obtuse, horizontally flattened apex (Pl. XVIII. fig. 3). The anterior 
border of the sternum (Pl. XVI. fig. 4.) is widely and rather deeply emarginate at 
the middle (e), less deeply so on each side: the breadth of the mid notch (4 ¢ d) is 
1 inch 9 lines, that of each side notch (6 d) is 1 inch 2 lines. The sternum is deeply 
hollowed above (Pl. XXIII. fig. 4), correspondingly convex beneath (ib.); the keel (s) 
is low and thick, commencing by a pair of broad obtuse ridges (Pls. XVI. fig. 4, & 
XVII. fig. 1, 7 7) from the mesial ends of the outer walls of the coracoid grooves 
