List of Plates. vii 



LXI. Trilobites from the Black River Formation. See explanation, 



p. 255. 

 LXII. Trilobites from the Black River and Trenton Formation. See 



explanation, p. 255. 

 LXIII. Aphelops montanus Douglass. 

 LXIV. Aphelops ceratorhinus Douglass. 

 LXV. Teeth of Fossil Horses from North Dakota and Montana. See 



explanation, p. 276. 

 LXVI. Skull of Merychippus missouriensis Douglass. See explanation 

 p. 276. 

 LXVII. Miocene Horses from Montana. See explanation, p. 276. 

 LXVIII. Miocene Horses from Montana. See explanation, p. 277. 



