592 



BRITISH FOSSIL REPTILES. 



bones of the extremities, especially of the metatarsals : and, above all, by the toes being 

 terminated by strong claws." Here, in 1842, tlie clavvless character of the limbs of 

 Plesio- and Ichthyo-sauri was the dominant idea, to the exclusion of the then novel 

 group of Dinosauria, " characterised by a large sacrum composed of five anchylosed 

 vertebrae of unusual construction," &c.* 



Tiie question to be determined in respect to Cetiosauriis is the admissibility of the 

 genus by the sacral character to the Dinosauriau order. This character, in 1842, I put 

 in the van, relating as it does, physiologically, to terrestrial progression more after the 

 manner of Mammalian quadrupeds than of existing four-footed Saurians, whether 

 Crocodiles or Lizards ; an extent of the trunk being thereby transmitted, through a 

 co-extensive ilium, upon hind limbs, the chief bones of which are ' medullary ' in 

 Dinosauria. 



Fig. 10. 



Ilium, Cetiosaurus longus, Jjth nat. size. (Phps., cv, p. 278.) 



The ilium (fig. 10) of the Cetiosaurus longus, from the Kirtlington quarry, is estimated 

 by Phillips as probably equal to six vertebrae. He writes : 



"The extreme length of one (ilium) is 42, of the other 45 inches, probably equal to 

 six vertebra?,"t — such sacral vertebra being estimated each at a little over 7 inches in 

 length. 



These vertebrae are briefly noticed as follows : — " Several bones of this portion are in 

 the collection, but there is great difficulty in so placing them as to acquire a just notion of 

 the structure or to present a satisfactory drawing. In some degree it (the sacrum) must 

 have approached that of Hi/Iceosaurus." % I found a nearer approach to the sacrum in 

 Scelidosaurus. 



In either comparison the length of the sacrum is not to be estimated as equal to that 

 of the ilium. In Scelidosaurus, e.g., in which the number of sacral vertebrae is ' four,' the 

 parts of tlie ilium anterior and posterior to the sacro-iliac symphysis, or surface of junction 

 with such vertebrae, give to that pelvic bone almost twice the length of the sacrum. The 

 length of this part of the spine in Scelidosaurus is 10 inches, whilst that of the ilium is 



* ' Report,' ut supra, p. 102. t Op. cit., p. 278. % Op. cit., pp. 257-8. 



