in North America of rare Extinct Vertebrates. 203 



of opposite sides are separated by a [bony] septum which 

 is thin medially"*. In the ' Paljeontological Bulletin/ 

 no. 28, the author writes, " the centra of the dorsal vertebrai 

 are hollow, including two large chambers which are separated 

 by a longitudinal wall "f. 



In regard to the " cervical vertebra," Prof. Cope speaks of 

 " the interior chambers "J as differentiating them from the 

 " dorsal centra," in which " there are but two chambers, 

 which are separated by a longitudinal median septum " §. 

 Such is the difference indicated in the more anterior and the 

 less anterior of the tnink-vertebrje from the Isle of Wight in 

 regard to my second character of Chondrosteosaurus. It does 

 not appear, however, that this largely cancellous stnicture was 

 investigated or exposed in the Colorado vertebrae, as in the 

 British Wealden ones, by special sections; allusion is only made 

 by Prof. Cope to the " broken centrum from which Mr. Lucas 

 had removed the matrix"!;. 



I believe myself justified nevertheless in concluding that 

 the characters, from internal stnictm'e as from terminal articu- 

 lations and lateral fossse, on which the genus Chondrosteo- 

 saunxs was founded, equally denote the " gigantic Saurian 

 from the Dakota epoch of Colorado." 



3. Costal Articidations. 



A third character, if an extinct reptile be indicated solely by 

 cervical or anterior dorsal vertebrae, is to be derived "from the 

 processes or surfaces which such vertebrse afford for the articu- 

 lation of the ribs. In modern Reptilia such processes are 

 single on each side in lizards, double in crocodiles. For 

 the needs of intelligible description of the numerous and varied 

 fossil vertebrae submitted to or observed by me in the course 

 of preparing my ' Report on British Fossil Reptiles ' (1840 

 and 1841), I proposed to call, in the vertebra showing 

 the double joint, the lower or capitular articular costal 

 process " parapophysis," the upper or tubercular one " diapo- 

 physis." 



In characterizing the Wealden fossils in question it is 

 written : — " That the vertebra is from the fore part of the tinink 

 may be inferred from the presence, on each side, of both a 

 parapophysis (plate ii. p) and a diapophysis (ib. c7), indica- 



* Loc. cit. p. o. 



t ' Proceedings of the American Philoeophical Society/ vol. xvii. 

 no. 100, May to December, 1877, p. 233. 



X Loc. cit. p. 334. 5 Loc. cit. p. 235. 



11 Pal. Bull. no. 25. p. 5, August 23, 1877. 



14* 



