246 0. 0. Marsh — Restoration of Camptosaurus. 



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, more- 

 over, are not coossified, even in adult forms, and to this char- 

 acter the name Camptonotus first given to the genus by the 

 writer in 1879 especially refers.* Another notable feature of 

 the sacral vertebrae 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 compensating in a measure 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 entirely unossified, and 

 no trace of clavicles has been found. The pelvis of Campto- 

 saurus 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 rudimentary, and the fifth entirely want- 

 ing, as shown in Plate YI. The entire skeleton of Campto- 

 saurus was proportionately more slender and delicately formed 

 than that of Iguandon, although the habits and mode of life 

 of these two herbivorous Dinosaurs were doubtless very similar. 



The type specimen of Ca?np>tosaurus dispar, used as the 

 basis of the present restoration, is from the Atlantosaurus beds 

 of the upper Jurassic of Wyoming. This species and other 

 allied forms will be described in full in an illustrated memoir 

 now in preparation by the writer for the United States 

 G-eological Survey. The present restoration is reduced from a 

 large drawing made for that volume. 



New Haven, Coim., February 23, 1894. 



* This name proved to be preoccupied, and Camptosaurus was substituted for 

 it. This Journal, vol. xxix, p. 169, February, 1885. 



