LIFE AND KINSHIP OF DINOSAURS. 605 



nally thick pectineal process ;* it unites distally with its fellow, and in some species also, 

 as in Monotremes, with the ischium, dividing the obturator space. The average pro- 

 portions and common character of the pubis in Laeertilia are given in Cut, fig. 15, 

 Monitor; the perforation d marks the closer resemblance to the Dinosaurian pubis 

 (fig.l2,;,4). 



Notwithstanding the difference in the proportions of breadth and length, the pubis in 

 IguanodoH and Omosaurus, in its essential characters, is more like that in the Tortoise 

 than in any bird. But these proportions are among the most variable characters of the 

 bone, and we have not far to seek in the Lacertian order before finding, as in Uromastix, 

 a pubis combining with the pectineal process (PI. 73, figs. 8 and 9, b), as slender a body 

 thence continued as in the Dinosaiiria. Only, in Omosaurus, the proximal end of the 

 bone seems not to contribute any share to the acetabular cavity ; and, if this should be 

 the case with other Dinosaurs, those extinct reptiles would combine, in their pelvis, as in 

 some other parts of their skeleton, characters now restricted respectively to the Croco- 

 dilian and to certain members of the Lacertian groups of the class. 



Thus, the ischium, in Omosaurus, has no other 'process ' save the stunted homologue 

 of the proximal extension supporting the pubis in Crocodilia. 



In Chdonia, as in Vromastix, there is a distinct posterior process (marked c in figs 

 8 and 9, PI. 73) ; but in certain Lizards {Varamis nilotkus, e. g.)t it is reduced to a mere 

 rudiment, and in the Chameleon it ceases to exist. Thus, the Omosaurus resembles the 

 Crocodilia and some Laeertilia in the simplicity of its ischium, and markedly departs 

 from the type of birds in respect to this bone. 



But it is alleged that the ilium gives evidence of the avian affinity of Dinosaurs -which 

 we have now proved to be wanting in the rest of the pelvis. Among the " points of 

 difference between any existing lleptile and any existing Bird," the following is put by 

 Professor Huxley in the foreground. 



" 1. In the Reptile the ilium is not prolonged in front of the acetabulum." " In the 

 bird the ilium is greatly prolonged in front of the acetabulum." 



" Now, in all the Binosauria which I have yet examined, the ilium extends far in 

 front of the acetabulum."! 



To the first of these averments it needs only an elementary acquaintance with compa- 

 rative osteology to reply, that in all Crocodilian Reptiles the ilium is pi'olonged in front 

 of the acetabulum, and to an extent nearly equal to that in which it is produced behind 

 the acetabulum. Reference to the well-known figure in the ' Ossemens Fossiles,' which I here 

 reproduce (woodcut, fig. 13, it) exemplifies this fact : Cuvier has been careful to mark with 

 the letter ' a ' the antacetabular part of the ilium which the advocate of the avian affinities 

 and bipedal progression of the Di/iosauria denies to it and to all other Reptiles, Diiiosauria 



* 'Anat. of Vertebrates,' vol. i, fig. 116, h. 



f Cuvier, ' Ossemens Fossiles,' torn, cit., pi. xvii, fig. 40, c. 



X 'Quarterly Jouru. Geol. See.,' vol. x.xvi, 1870, p. 26. 



