THE DINOSAUR! A. 
47 
are Macrurosaurus, Anoplosaurus, Syngonosaurus, Eucerco- 
saurus, and Acanthopholis. The last genus also ranges into 
the Chalk. On the Continent, after the Trias, Dinosaurs are 
rarely found. Thaumatosaurus from the Inferior Oolite is a 
species of Pliosaurus, and has no Dinosanrian characters. 
The Continental Wealden specimens are as yet nndescribed ; 
hut Professor Suess has found in the Gosau heels a rich Dino- 
saurian fauna, the general nature of which was briefly indicated 
by Dr. Bunzel. Professor Fritsch has figured a fragment of a 
Dinosaurian limb-bone from the Chalk of Bohemia, and long 
ago Dinosaurian bones were figured from the Maestricht beds, 
some of them closely conforming to the Iguanodont type. 
Nothing need be said now of the mauy American Dinosaurs 
described by Leidy, such as Ccelosaurus, Hadrosaurus, and 
Astrodon, which, together with Lselaps of Cope, occur in the 
Greensand of New Jersey; while in the Far West Professor 
Cope has found Agathaumus, Cionodon, and Polyonax. More 
recently there have been obtained from Colorado Camarasaurus 
of Cope, which appears to be identical with Atlantosaurus of 
Marsh, and is associated with genera named by the latter 
author Morosaurus, Apatosaurus, Allosaurus, and Diplodocus, 
and genera named by Cope Amphiccelias and Epanterias. It 
is, however, at present uncertain whether the latter genera 
are all distinct from the former. 
This great succession of animals exhibits a diversity of 
organization, exceeding, so far as can be judged from the 
bones, that observed in any existing order of reptiles. It is 
probable that in the long period of geological time the group 
underwent evolution, not merely in the sense of the skeleton 
becoming modified by being adapted to altered conditions of 
existence, forced upon the animals by changing forms of the 
land-surfaces of the world, but also in actual progress from 
a lower to a higher type. Yet, with all this diversity, there 
is rarely any difficulty in recognizing the distinctive Dino- 
saurian characteristics of the animals, as shown in the trans- 
verse platform of the neural arch from which the neural spine 
rises, in the form of the scapular arch, and the pelvic girdle, and 
the characteristic shapes of the principal bones of the fore and 
hind limbs. But when the Dinosaurs first appeared in the 
Trias, the difficulty of defining the limits of the order is great 
on account of the way in which many of the types approxi- 
mate to Crocodiles and other lower animals. In fact, the 
Triassic Crocodilia seem to foreshadow the Dinosaurs, though 
the two groups are contemporaneous. This is evident from 
the circumstance that Professor Owen formed the order Theco- 
dont ia to receive such types as the Thecodontosaurus, which 
Professor Huxley has shown to possess the essential charac- 
