224 DINOSAURS OF NORTH AMERICA. 



the distal end is projected well backward, indicating great freedom of 

 motion at the knee. 



The tibia is shorter than the femur and has a prominent cuemial 

 crest. The distal end is much flattened, and the astragalus is closely 

 adapted to it. The fibula is very straight, with its lower end flattened 

 and closely applied to the front of the tibia. The calcaneum is large, 

 with its concave upper surface closely fitted to the end of the fibula. 

 Of the second row of tarsals only a single one appears to be ossified, 

 and that is very small and thin, and placed between the calcaneum and 

 the fourth metatarsal, nearly or quite out of sight. 



The hind foot, or pes, had but three digits, the second, third, and 

 fourth, all well developed and massive. The terminal phalanges were 

 covered with broad hoofs. The first and fifth digits were entirely wanting. 



A comparison of the limbs and feet of Claosaurns, as here described 

 and figured, with those of three allied forms from the Jurassic, Stego- 

 sauius, Laosaurus, and Gamptosaurus, as shown on Pis. XLVIII, LIV, 

 ami LV, is especially instructive. These three genera have already 

 been quite fully described and figured by the writer, but new points 

 of interest have been made out by the recent investigation of more 

 perfect material. The present figures will show more accurately some 

 of the mutual relations of these early herbivorous dinosaurs to one 

 another, as well as to their successors in Cretaceous time. The gradual 

 changes that can be traced from one to the other will be discussed in 

 a later communication. 



All the limb bones in Claosaurus are solid, thus distinguishing it from 

 Trachodon ( Hadrosaurus). The separate ischium not coossified with the 

 pubis, the absence of a fourth digit in the hind foot, and other marked 

 characters, also make the genus distinct from Pteropelyx, the skull of 

 which is not known. 



RESTORATION OF CLAOSAURUS. 



Plate LXXIV. 



The reptile here restored was nearly 30 feet in length when alive, and 

 about 15 feet in height in the position represented in PI. LXXIV. 

 The remaius were obtained in the Ceratops beds of the Laramie, in 

 Wyoming. Among the associated fossils are the gigantic Triceratops 

 and Torosaurus, which were also herbivorous dinosaurs, and with them 

 were found the diminutive Cretaceous mammals recently described by 

 the writer. 



TRA CHODOXTIDJE. 



The geuus Trachodon of Leidy, which has been admirably described 

 under the name Hadrosaurus by that author, 1 is a near ally of Clao- 

 saurus, but quite distinct. The generic name Uiclonms Cope should 

 be regarded as a synonym of Trachodon. The teeth of one species of 

 this genus are shown in PI. LXXV, figs. 1 and 2. 



1 Cretaceous Reptiles of the United States, p. 76, 1865. 



