208 Prof. O. C. Marsh—Comparison of Dinosauria. 
found below the Jurassic. The Huskelesaurus of Huxley, 1867, from 
the Trias of South Africa, is apparently a member of this group. 
ORNITHOPODA. 
The great group which the author has called the Oraithapode is 
well represented in Europe by Iguanodon and its allies. The remark- 
able discoveries in the Wealden of Belgium, of a score or more 
skeletons of Iguanodon, have furnished material for an accurate study 
of the genus which they represent, and, indirectly, of the family. 
The genus Iguanodon, founded by Mantell in 1824, is now the 
best known of HKuropean forms, and need not here be discussed. 
Hypsilophodon, Huxley, 1870, from the Wealden, is likewise well 
represented, and its most important characters fully determined. 
The other genera of this group, among which are Mochlodon, Bunzel, 
1871, Vectisaurus, Hulke, 1879, Orthomerus, Seeley, 1888, and Spheno- 
spondylus, Seeley, 1883, are described from less perfect material, and 
further discoveries must decide their distinctive characters. 
None of these genera are known from America, but allied forms 
are not wanting. A distinct family, the Hadrosauride, is especially 
abundant in the Cretaceous, and another, the Camptosauride, includes 
most of the Jurassic species. The latter are the American repre- 
sentatives of the Iguanodontide. The nearest allied genera are, 
apparently, Iguanodon and Camptosaurus for the larger forms, and 
Hypsilophodon and Laosaurus for those of small size. A few isolated 
teeth from each country suggest that more nearly related forms may 
at any time be brought to light. 
Many generic names have been proposed for members of this 
group found in America and in Europe, but, in most cases, they are 
based on fragmentary, detached specimens, which must await future 
discoveries before they can be assigned to their true place in the 
order. 
As a whole, the European Ornithopoda now known seem to be 
less specialized than those of America, but additional discoveries 
may modify this opinion. The geological range of this group, so far 
as known, is essentially the same on each continent, being confined 
to the Jurassic and Cretaceous. There is some evidence, from foot- 
prints, at least, that, in America, the order was represented in the 
Trias. 
THEROPODA. 
The carnivorous Dinosauria have all been included, by the author, 
in one order, Theropoda, although there are two or three suborders 
quite distinct from each other. This great group is well represented 
both in Europe and America in the Trias, is especially abundant in 
the Jurassic, and diminishes in the Cretaceous, at the close of which, 
it apparently becomes extinct. 
The typical genus is Megalosaurus, Buckland, 1824, the type of 
which was the first Dinosaurian reptile described. Although its 
remains are comparatively abundant in Hurope, they have been 
found only in a fragmentary condition, and many important points 
in the structure of the skull and skeleton are still in doubt. 
