0. C. Marsh— Dinosaurs of N. America. 39 



luxe, which we hope the learned author will not long postpone to 

 bring out. 



In his brief Introduction, the author tells us that the true place of 

 the Dinosauria in the animal kingdom has been a matter of much 

 discussion amongst anatomists, but the best authorities now regard 

 them as constituting a distinct subclass of the Reptilia. Some of the 

 large, earlier forms are apparently related to the Orocodilia, while 

 some of the later small specialized ones have various points of 

 resemblance to birds. These diversified characters make it difficult 

 to classify the dinosaurs among themselves, and have led some 

 writers to assert that these reptiles do not form a natural group, 

 but belong to divisions remotely connected, and not derived from 

 a common ancestry. 



Without discussing in detail the classification of this group, it may 

 be stated in a few words that three great divisions of the Dinosauria 

 are generally recognized, which may be properly regarded as distinct 

 orders. For these groups the author has proposed the names 

 Thkropoda for the one including the carnivorous forms, and Sauro- 

 roBA and Pkedentata for the two herbivorous groups, the last order 

 being made up of three separate suborders, namely, the Stegosauria, 

 the Ceratopsia, and the typical Ornithopoda. The first of these sub- 

 orders contains large dinosaurs, more or less protected by a dermal 

 covering of bony plates; the second group includes the huge horned 

 dinosaurs ; and the third is made up of the forms that in shape and 

 structure most nearly resemble birds. 



Commencing with the Triassic deposits, we find that a dinosaur 

 {Clepsysaurus Fennsyhanicus, Lea) was made known from a few 

 bones, found in 1847, and described by Dr. Isaac Lea in 1851 ; and 

 a jaw with teeth, named Bathygnathus borealis by Dr. Leidy, from 

 Prince Edward Island, Canada, was described in 1854 (Journ. Acad. 

 Nat. Sci. Philad. 1853 and 1854). A third, named Megadactylus 

 polyzelus, was discovered by the veteran Professor E. Hitchcock 

 in 1856, and described in 1865 by his son, E. Hitchcock, jun. 



A nearly complete carnivorous dinosaur was discovered in 1884 

 in the same Connecticut River series of Triassic age, and named by 

 Marsh Anchisaurus colurus (see plates ii, iii, iv, op. cit., and 

 Geol. Mag. 1893, Fig. 1, p. 150). The foot of another Triassic 

 form (Ammosaurus) is also figured, and reference is made to 

 dinosaurian Triassic footprints, the so-called "bird-tracks" of the 

 Connecticut River series. The occurrence of Thecodontosaums in 

 the Trias of Bristol (England), and Plateosauriis (Zanclodon) 

 m Germany, completes the European and American Triassic forms, 

 but other remains have been found in India, in South Africa, and 

 in Australia. 



In the Jurassic strata of Colorado, Professor Marsh has discovered 

 a small Theropodous dinosaur of carnivorous habits, about the size 

 of a rabbit, in which the metatarsals of the hind-limbs are greatly 

 elongated, suggesting the generic name of Eallopus, or leaping-foot, 

 Irom its probable mode of progression. In another higher stratum 

 of the Colorado series the genus Coelurus is met with, of the same 



