List of Casts, Models, and Photographs. I 3 



Stage h. — Hyracotherium craspcdotum. Fore and hind feet. Middle 

 Eocene (Wind River), Wyoming. Fotir toes and a rudi- 

 ment of a fifth (ist digit) on the fore foot, three toes on 

 the hind foot. Size of a fox. Price, $4. 



Stage e. — Mesohippus hairdi. Fore and hind feet. Lower OUgocene 

 (White River), S. Dakota. Three toes on fore and hind 

 foot, the fourth (5th digit) represented on the fore foot by 

 a short " spHnt-bone." Lateral toes much reduced, but 

 still touching the ground. Size of a prairie wolf. 



Price, $4. 



Stage /'. — Mesohippus intermedius. Fore and hind feet. Upper Oli- 

 gocene (White River, Protoceras Beds), S. Dakota. Like 

 M. bairdi, but larger. Price, $5. 



Stage /". — Mesohippus copei. Hind foot. Upper Oligocene (White 

 River, Protoceras Beds), S. Dakota. Larger than M. 

 intermedius. Price, $j. 



Stage h". — Hypohippus equinus. Fore and hind feet. No. 8407 

 Middle Miocene (Loup Fork) , Colorado. Larger than any 

 of the preceding species; size of Shetland pony. Fifth 

 digit of the fore foot reduced to a little nodular rudiment. 

 Side toes still touch the ground. Price, $12. 



Stage i'". — Merychippus sejuncUis. Fore and hind feet. Middle Mio- 

 cene, Colorado. Fifth digit of fore foot a small nodular 

 rudiment, side toes much reduced, not reaching the 

 ground. Size of 3-months-old colt. Price, $10. 



Stage f". — Neohipparion whitneyi. Fore and hind feet. Upper Mio- 

 cene (Loup Fork), S. Dakota. Feet and limbs elongate, 

 proportions like those of the deer. Side toes more re- 

 duced than in Merychippus, size somewhat larger. 



Price, $12. 



30. Series of Fossil Horse Skulls. 

 Illustrating the Evolution of the Horse. 



(Stages corresponding with those in No. 29.) 



Those now ready are : 



Stage c.—Protorohippus venticolus. Crushed skull and jaws. No. 

 4832 From mounted skeleton in Cope Collection. Mid- 

 dle Eocene (Wind River), Wyoming. Short-crowned 

 teeth of primitive pattern. Size of fox. ^^_^^ ^^ 



