206 Prof. O. C. Marsh—Comparison of Dinosauria. 
to the humerus, portions of the osseous dermal covering, the first 
detected in the Sawropoda, and known only in the present specimen. 
A dozen or more generic names have been proposed for the 
European forms of Sawropoda, and of these Cetiosawrus, Owen, 
1841, is the earliest, and must be retained. The remains on which 
this genus was based are from the Great Oolite, or Lower Jurassic. 
Cardiodon, Owen, 1845,1 is from nearly the same horizon, and there 
appears no evidence that the two forms are not identical. Peloro- 
saurus, Mantell, 1850, is from the Wealden, and may be distinct, 
but, at present, the proof is wanting. Oplosaurus, Gervais, 1852, 
also from the Wealden of England, cannot well be separated from 
Pelorosaurus. Gigantosaurus, Seeley, 1869, from the Kimmeridge 
of the Upper Jurassic, may prove to be different from the above, 
but the type specimens alone do not indicate it. Bothriospondylus, 
Owen, 1875, is also from the Kimmeridge, and, although the type 
specimen pertains to a very young, if not foetal individual, it seems 
to be distinct, and may be nearly allied to the American genus 
Pleurocelus. The author failed to find conclusive evidence in the 
type specimens themselves for the use of the other generic names 
proposed, namely: Ornithopsis, Seeley, 1870, from the Wealden ; 
Eucamerotus, Hulke, 1872, Wealden; Ischyrosaurus (preoccupied), 
Hulke, 1874, Kimmeridge; and Chondrosteosaurus, Owen, 1876, 
Wealden. 
Aipyosaurus, Gervais, 1852; Macrurosaurus, Seeley, 1876; and 
Dinodocus, Owen, 1884, all represent forms from the Cretaceous, 
but their relations to each other cannot yet be determined. 
Discoveries of more nearly perfect specimens may establish the 
fact that the forms in the different geological horizons are distinct, 
but so long as the known remains are so isolated and fragmentary, 
this point must be left in doubt. 
The European Sauropoda at present known are from deposits 
more recent than the Lias, and none have been found above the 
Upper Greensand. In America, this group apparently has repre- 
sentatives in the Trias, was very abundant in the Jurassic, but, so 
far as now known, did not extend into the Cretaceous. 
STEGOSAURIA. 
Another group of Dinosaurian reptiles, which the author has 
called the Stegosauria, from the typical American genus Siego- 
saurus, is well represented in European deposits. The remains 
already discovered are more numerous, and in better preservation, 
than those of the Sawropoda, and the number of distinct generic forms 
is much larger. The geological range, also, is greater, the oldest 
forms known being from the Lias, and the latest from the Cretaceous. 
These reptiles, although very large, were less gigantic in size 
than the Sauropoda, and were widely different from them in their 
most important features. Their nearest allies were the Ornithopoda, 
to which they were closely related. 
1 Qardiodon dates from 1841 and Cetiosaurus also from 1841. See Introduction, 
Part 2, p. x, of Catalogue Fossil Reptilia, by R. Lydekker (May, 1889).—Enprr. 
