Procamelus occidentalis, Cope, (See Wheeler's Survey, vol. iv., Plate LXXVII.) Fig. 5.--Part of right maxillary and premaxillary, showing single incisor with rudimentary alveolus for a second. Protolabis ----? Cope. (See Wheeler's Survey, vol iv., p. 343.) Fig. 6.--Right maxillary and premaxillary. (This has never been drawn before, and was kindly lent to us for this purpose by Prof. Cope.) Camelus bactrianus. Modern camel. Fig. 7.--Right maxillaries, one half natural size. [Illustration] SYSTEMATIC CATALOGUE OF THE EOCENE VERTEBRATES OF WYOMING. Although we have endeavored to make this catalogue as complete and accurate as possible, we feel that errors and omissions are, from the nature of the case, unavoidable. The material is so vast and heterogeneous, and is so much scattered throughout numberless reports, bulletins, journals, and the like, that its correct compilation is attended with great difficulties. However, a beginning is here made which will render subsequent work easier. Owing to the great number of discoveries which have since been made, Dr. Leidy's excellent catalogue of 1871 covers now but a very small portion of the ground. In this list we have made no attempt to decide disputed questions of priority and synonymy. Doubtless, many of the genera and species here given will be found to be synonyms of American or European forms; but at present these questions cannot be settled. Where synonyms are given, they are the determinations of the original describer indicated in subsequent publications MAMMALIA. PRIMATES. Notharctus, Leidy. Pr. Ac. Nat. Sc., 1870, p. 114; Cont. to Ext. Vert. Faun., p. 86; Ann. Rep. U. S. Geol. Survey of Terrs., 1871, p. 364. _N. tenebrosus_, Leidy, loc. cit. Hyopsodus, Leidy. Pr. Ac. Nat. Sc., 1870, p. 110; U. S. Survey of Terrs., 1870, p. 354; do. 1871, p. 362; Cont. to Ext. Vert. Faun., p. 75. _H. paulus_, Leidy, loc. cit. _H. minusculus_, Leidy. Cont. to Ext. Vert. Faun., p. 81. _H. gracilis_, Marsh. Am. Journ. of Sci., vol. ii., p. 42. _H. vicarius_, Cope. Described in U. S. Survey of Terrs., 1872, p. 609, as _Microsyops vicarius_. Wheeler's Survey, vol. iv., pt. ii., p. 150. Microsyops, Leidy. Pr. Ac. Nat. Sc., 1872, p. 20; U. S. Survey of Terrs., 1871, p. 363; Cont. to Ext. Vert. Faun., p. 82. _M. gracilis_, Leidy, loc. cit. In the "Contributions," Dr. Leidy, considering _Limnotherium_, Marsh, as a synonym of _Microsyops_, has called this species _M. elegans_. Hipposyus, Leidy. Pr. Ac. Nat. Sc., 1872, p. 37; Cont. to Ext. Vert. Faun., p. 90. _H. formosus_, Leidy, loc. cit. _H. robustior_, Leidy Cont. to Ext. Vert. Faun., p. 93; _Notharctus robustior_. U. S. Geol. Survey of Terrs., 1871, p. 364. Antiacodon, Marsh. Am. Journ. of Sci., 3d Ser. vol. iv., p. 210. _A. venustus_, Marsh, loc. cit. Bathrodon, Marsh. Am. Journ. of Sci., 3d Ser. vol. iv., p. 211. _B. typus_, Marsh, loc. cit.