NO. lU(iU. OSTI'JOLOdV OF CAMPTOt^AURUS—aiLMORE. 301 



fn/ri/s" {Omof^aurus) from the Kimmeridge that Marsh believed 

 them to be identical. 



It is imfortunate that the early paleontologists rarely gave any 

 precise location, nuich less the exact geological horizon from which 

 typical specimens were obtained, so that the faunas of the upper 

 and lower parts of the American Jurassic, except in a few instances, 

 have never been differentiated. The whole fauna has been included 

 under the term Upper Jurassic, and only in the last few years have a 

 few authorities separated some of the upper part as lower Creta- 

 ceous. The vertebrates found in the Lakota at Buffalo Gap point to 

 its being the equivalent of the Wealden of England. xVssuming, as 

 many authorities do, that the Wealden is really Jurassic, these beds 

 would then represent the uppermost part of that formation. 



The above evidence, then, is in favor of the contemporaneity of the 

 Buffalo Gap horizon with the Wealden, and indicates that the age of 

 the Quarry 13 bone layer is greater than the Wealden. Such evi- 

 dence as is shown by the Camptosaurida^ not only supports Hatcher's 

 contention ^ that the lower members of the Morrison (Atlantosaurus 

 Beds) are below the Wealden, but that they are of greater age than 

 the Purbeck and jDossibly equivalent to the Kimmeridgian, 



RESTORATION OF CAMPTOSAURUS. 



Marsh gave us the first skeletal restoration of Caviptosaurus, here 

 reproduced as Plate 18. While this reconstruction gives a good 

 idea of the animal as a whole, it is now known, as has been pointed 

 out earlier in the present article, to be in error in several particulars. 

 The most striking change brought about by this more recent study is 

 the shortening of the presacral region, which was made too long by 

 Marsh, owing to an overestimate of the number of presacral vertebrae. 

 In his figure (see Plate 18) there are 30 presacral vertebrae, 9 of 

 which are considered as belonging to the cervical region, thus leaving 

 21 thoracic vertebra\ Two specimens in the U. S. National Museum 

 agree in having 16 dorsals each. If, then, this latter number is correct, 

 the presacral series would be shortened by 5 vertebrae, making the 

 proportions of the animal markedly different from the first conception 

 of its appearance (compare with Plate 19). Even though it ulti- 

 mately be found that Camptosaurus has 18 dorsal vertebrae (a possi- 

 bility indicated by the occurrence of that number in the holotype of 

 O. prestwichii and in the allied Iguanodon) , it would still mean the 

 shortening of the column by 3 vertebrae, which would have lessened 

 the distance between the fore and hind limbs, producing a more 

 comjDactly built animal than appeared in the first reconstruction, 



"Science (N. S.), XVI, 1902, p. 435. 



* Memoirs, Carnegie Musuem, III, 1903, p. 68, 



