Limnohyus, Leidy. Pr. Ac. Nat. Sc., 1872, p. 242; Cont. to Ext. Vert. Faun., p. 58; Marsh, Am. Jour. of Sc., 1872, 3d Ser. vol. iv., p. 124. _L. laticeps_, Marsh. _Palæosyops laticeps_. Am. Journ. Sc. 3d Ser. vol. iv., p. 122. _L. robustus_, Marsh, loc. cit., p. 124, is same as _P. major_, Leidy. _L. diaconus_, Cope. U. S. Geol. Survey of Terrs., 1872, p. 593. _L. fontinalis_, Cope, loc. cit., p. 594. Telmatherium, Marsh. Am. Jour. of Sc., 3d Ser. vol. iv., p. 123. _T. validum_, Marsh, loc. cit. Leurocephalus, gen. nov. This report, p. 42. _L. cultridens_, sp. nov. This report, p. 42. Hyrachyus, Leidy. Pr. Ac. Nat. Sc., 1871, p. 229; 1872, pp. 19, 163; U. S. Geol. Survey, 1871, p. 360; Cont. to Ext. Vert. Faun., p. 60. _H. agrarius_, Leidy, loc. cit.; _H. agrestis_. U. S. Survey, 1871, p. 357. _H. eximius_, Leidy. Pr. Ac. Nat. Sc., 1871, p. 229; 1872, p. 163; U. S. Geol. Survey of Terrs., 1871, p. 361; Cont. to Ext. Vert. Faun., p. 66; Cope, U. S. Geol. Survey of Terrs., 1872, p. 595. _H. modestus_, Leidy. Pr. Ac. Nat. Sc., 1872, p. 20; U. S. Geol. Survey of Terrs., 1871, p. 361; Cont. to Ext. Vert. Faun., p. 67; _Lophiodon modestus_, Pr. Ac. Nat. Sc., 1870. p. 109. _H. nanus_, Leidy. Pr. Ac. Nat. Sc., 3d Ser. 1872, p. 20; U. S. Survey, 1871, p. 361; Cont. to Ext. Vert. Faun., p. 67. _H. princeps_, Marsh. Am. Jour. of Sc., 3d Ser. vol. iv., p. 125. _H. implicatus_, Cope. On Some Eocene Mammals, p. 5; U. S. Survey, 1872, p. 604. _H. crassidens_, sp. nov. This report, p. 52. _H. imperialis_, sp. nov. This report, p. 50. _H. intermedius_, sp. nov. This report, p. 51. _H. paradoxus_, sp. nov. This report, p. 53. Helaletes, Marsh. Am. Jour. of Sc., 3d Ser. vol. iv., p. 218. _H. boöps_, Marsh, loc. cit. _H. latidens_, sp. nov. This report, p. 54. Lophiodon. _L bairdianus_, Marsh. Am. Jour. of Sc., 3d Ser. vol. ii., p. 36. _L. affinis_, loc. cit., p. 37. _L. nanus_, loc. cit. _L. pumilus_, loc. cit., p. 38. Lophiotherium. _L. sylvaticum_, Leidy. Pr. Ac. Nat. Sc., 1870, p. 126; Cont. to Ext. Vert. Faun., p. 69. _L. Ballardi_, Marsh. Am. Jour. of Sc., 3d Ser. vol. ii., p. 39. Orotherium, Marsh. Am: Jour. of Sc., 3d Ser. vol. iv., p. 217. _O. mintanum_, Marsh, loc. cit. Helohyus, Marsh. Am. Journ. of Sc., 3d Ser. vol. iv., p. 207. _H. plicodon_, Marsh, loc. cit. Thinotherium, Marsh. Am. Jour. of Sc., 3d Ser. vol. iv., p. 208. _T. validum_, Marsh, loc. cit. ARTIODACTYLA. All the forms described under this head are of uncertain reference. Elotherium. _E. lentum_, Marsh. Am. Jour. of Sc., 3d Ser. vol. ii., p. 39. Platygonus. _P. Ziegleri_, Marsh, loc cit., p. 40. Parahyus, Marsh. Am. Jour. of Sc., 3d Ser. vol. xii., 402. _P. vagus_, Marsh, loc. cit. Homacodon, Marsh. Am. Jour. of Sc., 3d Ser. vol. iv., p. 126. _H. vagans_, Marsh, loc. cit. Ithygrammodon, gen. nov. This report, p. 56. _I. cameloides_, sp. nov. This report, p. 57. AMBLYPODA.