262 THE ANATOMY OF VEKTEBEATED ANIMALS. 



what backwards, to unite with its fellow in a median ventral 

 symphysis. The obturator space is not interrupted by 

 any forward process of the outer and anterior half of the 

 ischium. 



In all birds (Fig. 78, A.), the ischium is elongated and 

 inclined backwards, the backward direction being least 

 marked in Apteryx, and most in Rhen. The ischia never 

 come together directly in a median ventral symphysis, 

 though they xmite dorsally in Bhea. The anterior edge of 

 the external, or acetabular, half of the ischium very gene- 

 rally sends off a process which unites with the pubis, thiis 

 dividing the obturator space. 



In all the Ornithoscelida (Fig. 78, B.), iu which I have been 

 able to identify the bone {Thecodontosawrus, Teratosaurus, 

 Megalosaunis, Iguanodon, Stenopelyx, Sadrosaurus, Hypsilo- 

 pliodon), the ischium is greatly elongated. In Igttanodon it 

 has the obturator process characteristic of the same bone in 

 Birds; and I imagine that the same process is seen in 

 Compsognathus. In Sypsilophodon there can be no mistake 

 about the matter, and the remarkable slenderness and pro- 

 longation of the ischium give it a wonderfully ornithic 

 character. In Iguanodon the slenderness and prolongation 

 are even carried beyond what is to be seen in Birds. I am 

 disposed to think, however, that, as was certainly the case 

 in Hypsilophodon, the ischia united in a median ventral 

 symphysis in all the Ornithoscelida. 



3. In all reptiles the pubis is inclined forwards, as well as 

 downwards, towards the ventral median line. In all, except 

 the Crocodile, it takes a considerable share in the formation 

 of the acetabulum ; and the ossified pubis unites directly 

 with its fellow in the middle line. 



The pubes of Compsognathus are, unfortunately, obscured 

 by the femora. They seem to have been very slender ; and 

 to have been directed forwards and downwards, like those 

 of lizards. Some lizards, in fact, have pubes which, if the 

 animal were fossilized in the same position as Compsogna- 

 thus, would be very similar in form and direction. Sypsilo- 

 phodon, however, affords unequivocal evidences of a further 



