194 Prof. 0. C. Marsh — Restoration of Camptosaurus. 



In comparing Camptosaurus, as here restored, witli a very perfect 

 skeleton of Iguanodon from Belgium, as described and figured, 

 various points of difference as well as of resemblance may be 

 noticed. The skull of Camptosaurus had a sharp, pointed beak, 

 evidently encased during life in a horny sheath. This was met 

 below by a similar covering, which enclosed the predentary bone. 

 The entire front of the upper and lower jaws was thus edentulous, 

 as in Iguanodon, but of different shape. The teeth of the two genera 

 are of similar form, and were implanted in like manner in the 

 maxillary and dentary bones. In Camptosaurus there is over each 

 orbit a single supra-orbital bone, curving outward and backward, 

 with a free extremity, as in the existing Monitor ; a feature not 

 before observed in any other Dinosaur except Laosaurus, an allied 

 genus, also from the Jurassic of America. Other portions of the 

 skull of Camptosaurus as well as the hyoid bones appear to agree 

 in general with those of Iguanodon. 



The vertebrae of Camptosaurus are similar in many respects to 

 those of Iguanodon, but differ in some important features. In the 

 posterior dorsal region, the transverse processes support both the 

 head and tubercle of the rib, the head resting on a step, as in 

 existing crocodiles. The five sacral vertebrae, moreover, are not 

 coossified, even in forms apparently adult, and to this character the 

 name Camptonotus first given to the genus by the writer in 1879 

 especially refers.^ 



Another notable feature of the sacral vetebree of the type specimen 

 should be mentioned. The vertebrae of the sacrum, especially the 

 posterior four, are joined to each other by a peculiar peg and notch 

 articulation. The floor of the neural canal of each vertebra is 

 extended forward into a pointed process (somewhat like an odontoid 

 process), which fits into a corresponding cavity of the centrum in 

 front. This arrangement, while permitting some motion between 

 the individual vertebrae, helps to hold them in place, thus com- 

 pensating in part for absence of ankylosis. A similar method of 

 articulation is seen in the dermal scales of some ganoid fishes, but, 

 so far as the writer is aware, nothing of the kind has been observed 

 before in the union of vertebrae. 



In Camptosaurus the sternum was apparently unossified, and no 

 trace of clavicles has been found. The pelvis of Camptosaurus 

 differs especially from that of Iguanodon in the pubis, the postpubic 

 branch being even longer than the ischium, while in Iguanodon 

 this element is much shortened. 



In the fore foot of Camptosaurus there were five functional digits, 

 the first being flexible and nearly parallel with the second, thus 

 differing from the divergent, stiff thumb of Iguanodon. The hind 

 feet had each three functional digits only, the first being rudi- 

 mentary and the fifth entirely wanting, as shown in Plate VI. 

 The entire skeleton of Camptosaurus was proportionately more 

 slender and delicately formed than that of Iguanodon, although the 



^ This name proved to be preoccupied, and Camptosaurus was substituted for it. 

 — American Journal, vol. xsix. p. 169, February, 1885. 



