202 Prof. R. Owen on the Occurrence 



This opinion is grounded on the following concordancies of 

 the characters w^hich I assigned to the genus with those noted 

 by Prof. E. D. Cope in a seemingly homologous vertebra, 

 which he terms " cervical," and which was submitted to his 

 examination by Mr. Lucas. 



1. Terminal Articulations of Centrum. 



The first character which I assigned to Chondrosteosaurus 

 was founded on the form of the terminal articular surfaces of 

 the centrum. " The hemispheroid convexity of the anterior 

 end (a) " was proved to be such, notwithstanding some abra- 

 sion of the fossil, " by the more perfect preservation of that 

 surface in the opposite concave articular end, ^ (plate iii.) "*. 



The vertebrae, at least at the fore part of the trunk, were 

 thus of the type which I have characterized as " opistho- 

 ccelian "f. 



Prof. Cope states that " a cervical and three dorsal verte- 

 bra " of the Saurian here compared " have a ball-and-socket 

 articulation of the opisthocoelian type "J. This character, 

 however, in parts of the vertebral column is common to other 

 genera {Strej)tosj>07idf/lnSy CetiosauruSy Iguanodon^ e. g.)§. 



2. Osseous Structure. 



The next character of Chondrosteosaurus is taken from the 

 osseous structure of the vertebrae. It was yielded by " the 

 large cancclli obvious at every fractured surface of the verte- 

 bra," and v/as further tested and exemplified by " a vertical 

 longitudinal section of a rolled and worn centrum of a second 

 anterior trunk-vertebra, figured three fourths of the natural 

 size in plate v. fig. 2"||. Of these cancelli it is remarked, 

 •' I deem it much more probable that they were occupied in 

 the living reptile by unossified cartilage or chondrine than by 

 air from the lungs " 1|. They might be termed, from their size, 

 huge internal sinuses. 



So Prof. Cope writes, " A broken centrum, from which Mr. 

 Lucas removed the matrix, shows tliat tliis foramen communi- 

 cates with a huge internal sinus, which occupies almost the 

 entire half of the body of the centrum. Those [sinuses] 



* Monogr. cited, p. 5. 



t Reports on British Fossil Reptilia, passim ; Anat. of Vertebrates, 

 8vo, vol. i. p. 59 ; and ' Palaeontology/ 8vo, p. 300. 



:t: "On a gigantic Saurian from the Dakota Epoch of Colorado," in the 

 Palseontological Bulletin, no. 25, 8vo, p. 5, published August 23, 1877. 



§ Report on British Fossil Reptiles, pt. ii. 1841, pp. 88-102. 



II Monogr. cited, pp. 6, 7. 



f Ibid. p. 6. . 



