Figuee 41. Skeleton of Neohipparion whitneyi. 



" 42. Hind foot and fore foot of Mesohippus intermedins. 



" 43. Evolution of the foot in the Horse family. 



" 44. Fore foot of the earliest known one-toed horse. 



" 45. Skull of Parahippus nebrascensis. 



" 46. Skull of Pliohippus lullianus. 



" 47. Phylogeny of the Horses. 



" 48. Evolution of the Horse. 



u 49. Skull of Megacerops marshi. 



" 50. Skull of Brontotherium platyceras. 



" 51. Male and female skulls of Titanotherium elatum. 



" 52. Skeleton of Megacerops robustus. 



" 53. Skeleton of Titanotherium prouti. 



" 54. First and last known stages in the evolution of the Titan- 



otheres. 



" 55. Skull and lower jaws of Dinohyus hollandi. 



" 56. Palatal view of skull of Dinohyus hollandi. 



" 57. Skeleton of Elotherium (Entelodon) ingens. 



" 58. Skeleton of Dinohyus hollandi. 



" 59. Upper and lower jaws of Desmathyus (Thinohyus) Sioux- 



ensis. 



" 60. Skull of Hyopotamus (Ancodus) brachyrhynchus. 



" 61. Skeleton of Hyopotamus (Ancodus) orachyrhynchus. 



" 62. Skeleton of Agriochoerus latifrons. 



" 63. Skeleton of Promerycochoerus carrikeri. 



" 64. Skeleton of Leptauchenia decora. 



" 65. Skeleton of Leptomeryx evansi. 



" 66. Fore and hind foot of Protoceras. 



" 67. Skull of Syndyoceras cooki. 



" 68. Skull of Poebrotherium wilsoni. 



" 69. Skeleton of Oxydactylus longipes. 



" 70. Phylogeny of the Camels. 



" 71. The Evolution of the Camel. 



" 72. Skeleton of Blastomeryx advena. 



" 73. Head of Stylemys nebrascensis. 



" 74. Part of the head of Crocodilus prenasalis. 



" 75. Head of Caimanoides visheri. 



Plate 1. The Gateway, School of Mines Canyon. 



2. Map of the White River Badland Formations of the Black 



Hills Region. 

 " 3. Columnar section of the Black Hills Region. 

 " 4. Earliest published view of the White River Badlands. 

 " 5. Hayden's early view of the Big Badlands. 

 " 6. Hayden's earliest geological map of the Upper Missouri 



country. 

 " 7. Hayden's second geological map of the Upper Missouri 



country. 



