PROFESSOR OWEN ON THE GENUS DINORNIS. 367 
lower margin ; the seventh blends with a smooth ridge-like thickening of the lower border 
of the acetabulum as it passes to be continued into the origin of the ischium (63). 
There then follow three sacrals without ‘ parapophyses;” a side view of these, 
defined by the double intervertebral foramina, is given from a fragment of a second 
pelvis at fig. 3, Pl. XLIII. In the eleventh sacral the lower process is suddenly resumed, 
passing obliquely outward and backward, straight to its confluent abutment against the 
postacetabular wall of the ilium; from this a continuous plate of bone curves inward 
and backward, with the lower margin bending forward to receive the expanded ends of 
the shortening parapophyses of the twelfth, thirteenth, and fourteenth, as well as of 
the eleventh, sacrals. The lower processes of the succeeding vertebre are more or less 
broken away. ‘The curved and bent lamelliform process of the ilium divides the inter- 
acetabular renal fossa from the ilio-ischial fossa behind. This (Pl. XLII. fig. 2, 7) is 
remarkable for its size, depth, and smooth surface, so far as it is preserved. 
Fracture of the fore part of the right ilium exposes the neural spine of the first 
sacral (fig. 2,8). It is directed upward and forward, is 1 inch 5 lines in height, 
7 lines from before backward, where it becomes free; and it terminates in a slightly 
expanded truncate border, which has contracted no anchylosis with the over-arching con- 
fluent iliac bones. The anterior articular surface of the first sacral (Pl. XLII. fig. 3, ¢) 
is, as usual, concave transversely, convex vertically, but almost bilobed in form from 
a shallow emargination below and the down-sinking of the neural canal above; its 
breadth is 11 lines, its mid vertical diameter but 3}limes. The neural canal is circular, 
24 lines in diameter. The prezygapophyses (ib. z z) look upward, inward, and rather 
forward ; they are each 6 lines in diameter ; together, an inch across their outer margins. 
The fore part of the base of the spine is impressed with a rough laterally ridged surface 
for the interneural ligament. The beginning of the inferior ridge represents a short 
“ hypapophysis”’ in the front view (Pl. XLII. fig. 3,4). The vertical extent of the 
fore part of the first sacral is 2 inches 3 lines; from the lower ridge to the upper part 
of the coalesced ilia is 2 inches 6 lines. The extreme breadth of the fore part of the 
pelvis, which is that of the first sacral across its diapophysis, is 1 inch 11 lines. The 
neural canal of the sacrum expands, as usual, as it extends backward, chiefly transversely 
(Pl. XLIII. fig. 4, 2), then contracts to the diameter shown at n, fig. 1, Pl. XLII. 
The ilia (Pl. XLII. fig. 1, 62), anterior to the acetabulum, ascend from their outer 
margins and converge rapidly to contact and partial confluence with the bases or mid 
parts of the sacral spines, above which they coalesce and form a ridge, the contour of 
which describes a moderate convex curve from before backward. The ridge, which is 
about 4 lines across anteriorly, narrows as it recedes. ‘The outer surface of the preace- 
tabular part of each ilium is uniformly concave, and the concavity is continued, con- 
tracting, above the acetabulum (a). The “gluteal ridges” (Pl. XLII. fig. 1, 7), which 
divide the concave tract (62) from the expanded convex or undulated tracts of the ilia, 
called “ pelvic disk” (7 7), rise as they recede and diverge, terminating rather abruptly 
