O. C. Marsh — Ornithopoda of the American Jurassic. 85 



Art. XI. — The Typical Ornithopoda of the American 

 Jurassic ; by O. C. Marsh. (With Plates IV- VII.) 



The herbivorous Dinosaurs now known from the Jurassic 

 deposits of this country consist mainly of the gigantic 

 Sauropoda and the* huge Stegosauria, both quadrupedal forms. 

 A third group is the bipedal Ornithopoda, which contains the 

 genus Camptosaurus as well as various smaller and more 

 bird-like types. The first two groups have been investigated 

 by the writer, and the main results published in this Journal. 

 The third group also received considerable attention during 

 the above investigation, but a recent study both of the type 

 specimens and additional material has revealed new points of 

 interest, and some of these are given in the present article. 



Camptosaurus, Marsh, 1885. 



The large Dinosaur described by the writer as Camptosau- 

 rus dispar, of which a restoration also has recently been pub- 

 lished,* is now so well known that it may be taken as a form 

 typical of the group. It is exceeded in size by Camptosaurus 

 amplus, Marsh, but there are at least two smaller species of the 

 genus (C. medius and C. nanus, noticed below). So far as 

 at present known, these species are found in successive deposits 

 of the same general horizon, the smallest below and the largest 

 above. 



Camptosaurus amplus is represented by remains which 

 show that this reptile when alive was about thirty feet in 

 length. The type specimen of C. dispar was about twenty 

 feet in length, and ten feet in height. C. medius was about 

 fifteen feet long. The smallest species of the genus, C. nanus, 

 was not more than six feet in length, and perhaps four feet in 

 height when standing at rest. One of the striking features of 

 this diminutive species is its long sigmoid scapula shown in 

 figure 3, Plate V. This is in strong contrast with the short, 

 straight scapula of C. dispar, seen on the same plate, figure 2. 

 The limb bones of all the species of this genus are very hollow. 



* This Journal, vol. xlvii, p. 245, March, 1894. See also, vol. xviii. p. 501, 

 December, 1879; and vol. xxix, p. 169, February, 1885 



