Prof. O. C. Marsh—Comparison of Dinosauria. 209 
The oldest representatives of this group in Europe are Thecodonto- 
saurus, Riley and Stutchbury, 1836, and Plateosaurus, von Meyer, 
1887, both from the Trias. The former genus is from the lower 
horizon, near Bristol, England; the latter, from the Keuper of 
Germany. Zanclodon, Plieninger, 1846, is from the same horizon as 
Plateosaurus, and appears to be the same thing. Massospondylus, 
Owen,.1854, from the Trias of South Africa, is “apparently a form 
allied to Thecodontosaurus. The nearest American genus is Anchi- 
saurus, two species of which are known from the Connecticut River 
sandstone. 
The most interesting member of the Theropoda known in Hurope 
is the diminutive specimen described by Wagner, in 1861, as 
Compsognathus longipes. ‘The type specimen, the only one known, 
is from the lithographic slates of Solenhofen, Bavaria, and is now 
preserved in the Museum in Munich. Fortunately, the skull and 
nearly all the skeleton are preserved, and as it has been studied by 
many anatomists, its more important characters have been made out. 
It is regarded as representing a distinct suborder, and no nearly 
related forms are known in Hurope. Its nearest ally is probably the 
specimen from Colorado, described by the author, in 1881, as Hallo- 
pus victor. This animal was about the same size as Compsognathus, 
and resembles it in some important features. It is probably from 
nearly the same geological horizon, but may be somewhat older. 
Hach of these specimens appears to be unique, and until a careful 
comparison of the two is made, their relations to each other can only 
be conjectured. 
The American representative of Megalosaurus is apparently Allo- 
saurus, a genus established by the author, in 1877. The type 
specimen is from Colorado, from a higher horizon in the Jurassic 
than that of Megalosaurus. Nearly every part of the skeleton of 
this genus is now known, and the more important portions have 
been described and figured by the author. Creosaurus, also from 
the Jurassic, is an allied form, and Dryptosaurus, from the Cretaceous, 
is, perhaps, also closely related. A very distinct form in the Jurassic 
is Labrosaurus, described by the author, in 1879. It is known from 
detached specimens only, but these, especially the jaws, edentulous 
in front, show it to represent a distinct family. 
The most perfectly known of American Theropoda, and by far the 
most interesting, is the genus Ceratosaurus, founded by the author, 
in 1884. ‘This is the representative of a very peculiar family, which 
differs in some important respects from all other known Dinosaurs. 
The skull and nearly all the various parts of the skeleton are known. 
When found, they were entire, and in the position in which the 
animal died. The skull and some of the more interesting parts of 
the skeleton have been figured by the author, and all will soon be 
fully described. 
The skull bears a large alevated horn-core on the median line of 
the nasals. The cervical vertebra differ in type from those of any 
other known reptiles, having the centra plano-concave. All behind 
the axis have the anterior end of each centrum perfectly flat, while 
DECADE III.—VOL. VI.—NO. V. 14 
