Lo 
30 MR. W. P. PYCRAFT ON THE MORPHOLOGY AND 
is convex, and forms, with its fellow of the opposite side, a long tunnel divided into 
right and left halves by the neural spines of the synsacrum, which acts as a median 
partition. 
The dorsal plane, which in Dromeus, Casuarius, and Rhea was restricted to a small 
area between the supra-trochanteric processes, here, in Struthio, extends backwards to 
the extreme end of the post-acetabular ilium, though it is very narrow. Furthermore, 
this plane slopes gently downwards on either side, so that its extremest outer angles 
approach the anti-trochanter. 
The pre-acetabular ilium meets in the mid-dorsal line above the synsacral spines: the 
post-acetabular ilia remain widely separated one from another throughout the greater 
part of their length ; in old individuals they meet and fuse with the last two post- 
sacral vertebre of the synsacrum. Down the median space, between the two post- 
ilia, runs a long bony bar, formed by the fusion of anterior and posterior ossifications 
of the neural spines. In Dinornithide, it will be remembered, it was pointed out [1] 
the equivalent ossifications extended laterally, so as to reach the ilia on either side, and 
thus close what would otherwise form a deep lateral trench lying on either side of the 
synsacrum. ‘This trench in Struthio remains permanently open. 
The ischivm is very slender and rod-shaped. At its posterior extremity it sends 
downwards a broad plate of bone which fuses with the pubis. In the young bird, it 
should be mentioned, the ischium is free posteriorly. The post-acetabular ilium and 
the ischium remain widely separated throughout life. 
The pubis is long, slender, and rod-shaped. In the adult it extends caudad far 
beyond the post-ilium and ischium, and curving sharply downwards and forwards, meets 
its fellow of the opposite side in the middle line, and becomes permanently fused 
therewith in a long, forwardly directed symphysis. This fusion of the pubes posteriorly 
occurs in no other living bird. 
As is well known now, the pubis of Strvthio is further remarkable for a small bony 
plate, attached to the middle of its ventral border by cartilage. In macerated 
skeletons this is generally lost; in this case its position is indicated by a roughened 
surface. 
This bone appears to have been originally described by Meckel [56], who held it to 
represent the marsupial bone of the Marsupials. More than forty years later this bone 
was rediscovered and described by Garrod and Frank Darwin [28]. They also regarded 
it as probably homologous with the marsupial bone of the Kangaroo and its allies. 
With this view Beddard [7] seems also to agree. 
The pectineal process is long, slender, and curved, its free end being directed 
upwards. 
The ilio-ischiadic fissure remains permanently open in Struthio. In Casuarius and 
Dromeus and in hea it closes later in life. The obturator fissure is closed, by fusion 
