PROFESSOR OWEN ON THE GENUS DINORNIS. 245 
augments to 1 inch 2 lines in the eleventh (ib. 11); thence this dimension gradually 
decreases to the breadth of 7 lines in the seventeenth sacral (ib. 17), slightly increasing 
in the eighteenth (ib. 18), which presents the characters of a coalesced caudal vertebra. 
The neural spines of the sacrals are confluent throughout; that of the first, 2 inches 
2 lines in length, has part of its summit (PI. LIII. fig. 2, s 1) exposed at the angle of 
divergence of the ilia (ib. 62); the following ten spines have coalesced with each other 
and with the upper or neural margins of these bones; the succeeding similarly coalesced 
sacral spines do not reappear until the divergence of the ilia (ib. 62*) at the eleventh 
sacral vertebra. The summits of the neural spines thence to the fifteenth vertebra 
are exposed to form a flat horizontal plate (ib. m, s), the side borders of which coalesce 
with mesial ones of the diverging ilia; this coalescence ceases at the spine of the 
fifteenth sacral, whence the coalesced flattened summits of the rest converge to the 
eighteenth, terminal vertebra (ib. 18). The thick pleurapophyses (ib. pl) of the last 
three sacrals are exposed at the interspaces between their spines and the iliac bones. 
The outer surface of the anterior two thirds of the ilium (ib. fig. 1, 62) is smooth, 
moderately concave, marked by a few vascular grooves; it forms the upper three 
fourths of the acetabulum (ib. a), and the surface (2) for the femoral trochanter con- 
tinued therefrom backward and upward; this surface is feebly concave vertically, convex 
lengthwise. The outer surface of the ilia behind their divergence is bent downward 
at a right angle with the horizontal flattened part; the extent of the downbent part 
( 62') is 4 inches, its vertical diameter is 1 inch; but this part of the bone is triedral, 
the third and inner surface inclining downward and inward to receive the coalesced 
ends of the abutting processes of the fourteenth to eighteenth vertebre inclusive. 
The admeasurements of the pelvis give the chief ones of the iliac bones. 
The ischium (63), after contributing part of the lower and hinder wall of the aceta- 
bulum, contracts to a subcylindrical bar of 6 jlines diameter and of like length ; it 
then expands with the lower border almost in contact with the pubis (64), the opposed 
rough surfaces indicating a fibrous union there 6 lines in extent, defining the hole (9) 
for the passage of the tendon of the ‘obturator internus’ muscle. Beyond this the 
ischium loses thickness and gains in breadth, attaining that of 2 inches at its free 
hinder end (63'); this is 1 inch distant from the ilium above, and 3 an inch from the 
free end of the pubis below. The ischia bend slightly inward towards their expanded 
ends, which are 33 inches apart at the upper angle, and 5 inches at the lower angle of 
the bone. 
The pubis (64), contributing the lower and fore part of the acetabular wall, contracts 
to a thickness of 5 lines, and assumes beyond the obturator foramen (qg) a subtriedral 
figure, flattened on the outer facet, and slightly expanding at its terminal upcurved 
extent of one inch and a half to a depth or breadth of 8 lines ( 6v ), with an interspace 
between it and the ischium of 5 lines. 
The cavity of the acetabulum (a) presents the usual circular form, with a diameter 
