CLASSIFICATION. 1 1 



In accepting the terms Theropoda and Sauropoda rather than Megalosauria and Opistho- 

 coelia or Cetiosauria, I do so out of regard for the more comprehensive nature of those terms 

 as used by Marsh. The latter terms as used originally by Fitzinger (Megalosauri), 1843, 

 Owen, 1859, and Seeley, 1874, respectively, I consider of subordinal rank only. Predentata 

 of Marsh is preferable to Orthopoda Cope, because it is in no sense coordinate with the latter, 

 but is a much more comprehensive term. Cope's Orthopoda and the Ornithopoda of Marsh (not 

 Huxley) are more nearly synonymous. 



The Ceratopsia constitute a well-defined and rather compact group, which falls naturally 

 within the Predentata as that order has been defined by Marsh. It embraces forms which in 

 many respects are the most highly specialized representatives of the Dinosauria yet discovered. 

 Marsh has considered the group as a suborder and defined it as follows: 



Premaxillaries edentulous; teeth with two distinct roots; skull surmounted by massive horn cores; a rostral bone, form- 

 ing a sharp, cutting beak; expanded parietal crest, with marginal armature; a pineal foramen (?). Vertebra? and limb bones 

 solid; fore limbs large, femur longer than tibia; feet ungulate; locomotion quadruped. Dermal armor. 



The above characters may be amended and supplemented as follows: Incipient teeth 

 with single roots, which later become completely divided into two branches by replacing teeth; 

 no true pineal foramen; dermal armor exceedingly imperfect; three [four, R. S. L.] a anterior 

 cervicals coossified; blade of ilium horizontal; post-pubis much reduced; ulna with well-devel- 

 oped olecranon process; rudimentary fourth trochanter on femur. 



There is nothing new or original in the above scheme of classification. It is that used by 

 Marsh in his "Dinosaurs of North America,"* and may be taken as representing his latest and 

 most mature views on that subject, with which, in the later years of his life, he was most inter- 

 ested. It is used here in preference to the more recent classifications of other authors, because, 

 in my opinion, it represents more nearly than any of these what is at present actually known 

 of the structure and relations of the various groups of the Dinosauria to one another and to the 

 Reptilia in general. 



All the Ceratopsia at present known pertain to one family, Ceratopsidae Marsh (=Aga- 

 thaumidse Cope). I accept the family name Ceratopsida? of Marsh rather than Agathaumida? 

 of Cope, because the former has priority and the genus Ceratops, upon which it was founded, 

 can not be shown to be a synonym of any of Cope's genera. 



ALPHABETICAL LIST OF GENEEA AND SPECIES. 



For convenient reference I give below a complete list, arranged alphabetically, of- all the 

 various genera and species that have at different times and by different authors been referred 

 to the Ceratopsia, with a reference to the original descriptions of each and present location of 

 the type. 



A. Agaihaumas Cope. Proc. Am. Philos. Soc, vol. 12, 1872, pp. 481-483. 



1. A. sylvestris. Proc. Am. Philos. Soc, vol. 12, 1872, p. 483. Type No. 4000, American Museum Natural History. 



2. A. rnilo Cope. Bull. 1, ser..l, U. S. Geol. and Geog. Surv. Terr., p. 10. Type in American Museum Natural His- 



tory; not identifiable. 



B. Ceratops Marsh. Am. Jour. Sci., 3d ser., vol. 36, Dec, 1888, pp. 477-478. 



3. C. (Bison) alticornis Marsh. Am. Jour. Sci., 3d ser., vol. 34, Oct., 1887, pp. 323-324, and Am. Jour. Sci,, 3d ser., 



vol. 37, Aug., 1889, pp. 174-175. Type No. 1871 E, U. S. National Museum. 



4. 0. horridus Marsh. Am. Jour. Sci., vol. 37, Apr., 1889, p. 334. — Triceratops horridus, Am. Jour. Sci., vol. 38, Aug., 



1889, pp. 173-174. Type No. 1820, Yale Museum. 



5. 0. montanus Marsh. Am. Jour. Sci., vol. 36, Dec, 1888, pp. 477-478. Type No. 2411, U. S. National Museum. 



6. C. (Eadrosaurus) paucidens Marsh. Am. Jour. Sci., vol. 37, Apr., 1889, p. 336, and Am. Jour. Sci., vol. 39, Jan., 



1890, p. 83. Type in the U. S. National Museum. 



C. CUwrKynchus Cope. Am. Naturalist, vol. 26, p. 757. 



7. C. trihedrus Cope. Am. Naturalist, vol. 26, pp. 757-758. Type No. 397S, American Museum Natural History. 



oSeep. 47. i> See Sixteenth Ann. Rept. U. S. Geol. Survey, pt. 1, 1896, pp. 237-244. cSeep. 100. 



