O. C. Marsh—On Dinosaurian Reptiles. 483 
Art. LV.—On_ the Affinities and Classification of the 
| Dinosaurian Reptiles ;* by O.C.Marsu. (With Plate X°) 
INTRODUCTION. 
For several years I have been engaged in the study of the 
Dinosaurs of North America, and the main results of the 
investigation have been published both in that country and in 
Europe. The material for this study consisted of the exten- 
sive collections made during my explorations in western North 
America, especially in the Rocky Mountain region, and the 
type specimens are nearly all preserved in the museum of Yale 
University. I first attempted in 1881 to make a classification 
of the series of specimens thus secured, and in the following 
year I extended this classification to include the European 
forms, and again in 1884 I expanded it still further to include 
all the Dinosauria then known.t+ 
Since that time, many new discoveries have been made, and 
some very strange forms have been brought to light in Amer- 
ica, which render a revision of this classification necessary. 
Besides the American forms, I have studied with care nearly 
every important specimen of Dinosaurs preserved in the 
museums of Europe, and as a result of all this investigation, I 
shall present to you an abstract, bringing the subject down to 
date. This will include a short statement as to the affinities of 
the Dinosaurs, so far as I have been able to make them out, 
and a synopsis of the classification, based mainly upon the char- 
acters of the Dinosaurs I have myself examined. 
To bring the subject directly before you, I have prepared 
the chart here shown (Plate X), which gives restorations of the 
skeletons of the twelve best known Dinosaurs, so far as I have 
been able to reconstruct them. Of these twelve forms, eight are 
from America; Anchisaurus, a small carnivorous type from 
the Trias; Brontosaurus, Camptosaurus, Laosaurus, and 
Stegosaurus, all herbivorous, and the carnivorous Cerato- 
saurus, from the Jurassic; with Claosaurus and Triceratops, 
herbivores from the Cretaceous. These American forms, with 
four from Europe, types of the well-known genera Compsog- 
nathus, Scelidosaurus, Hypsilophodon, and Lguanodon, com- 
plete the series represented on this chart. They form together 
an instructive group of the remarkable Reptiles we are now 
considering. 
* Abstract of paper read before the International Congress of Zoologists, at 
Leyden, September 17, 1895. 
+ This Journal, vol. xxi, p. 423, May, 1881; vol. xxiii, p. 81, January, 1882; 
Report British Association for the Advancement of Science, for 1884, p. 763. 
Am. Jour. Sci—Tasirp Series, Vou. L, No. 300.—DECEMBER, 1895. 
