276 Annals of the Carnegie Museum. 



Length of P3 18.5 



Length of P T 17.5 



Length of M T 15.5 



Length of M^ 16 



Length of M 5 21 



Length of femur 247 



Transverse diameter of femur 21 



Antero-posterior diameter of femur 31 



Length of median metapodial 165 



Width of median metapodial 18 



Proportion of transverse diameter to length of femur = 8.5 : 100. Transverse 

 diameter to length of median metapodial 10.9 : 100. 



Explanation of Plate LXV. 

 Fossil Horses from the Oligocene Deposits of North Dakota and Montana. 

 All figures twice natural size. 



Fig. 1. Mesohippus portentus? No. 1633. Two lower teeth in portion of a 

 mandible. 



Fig. 2. Mesohippus portentus sp. nov. Type. No. 1622. A right upper molar. 

 Crown view. 



Fig. 3. Mesohippus portentus sp. nov. Type. No. 1622. The same as Fig. 2. 

 Anterior view of tooth. 



Fig. 4. Mesohippus portentus ? No. 1623. A fourth left upper molar. Crown 

 view. 



Fig. 5. Mesohippus brachystylus ? Osborn. No. 1639. Anterior view of crown 

 of tooth. 



Fig. 6. Mesohippus brachystylus ? Osborn. No. 1639. Crown view. 



Fig. 7. Mesohippus hypostylus ? Osborn. No. 1625. Right upper molar. Crown 

 view. 



Fig. 8. Mesohippus hypostylus? Osborn. No. 1625. Anterior view. 



Fig. 9. Mesohippus hypostylus ? Osborn. No. 1635. Lower teeth. External 

 view. 



Explanation of Plate LXVI. 

 Skull of Merychippus missouriensis sp. nov. 



Type. No. 905. From Upper Miocene deposits. From Missouri Valley, east of 

 Winston, Montana. 

 One-half natural size. 



Explanation of Plate LXVI I. 

 Miocene Horses from Montana. 



All figures are one half natural size. 



Fig. 1. Merychippus insignis ? Leidy. No. 1377. From Deep Creek southeast 

 of Townsend, Montana. Lateral view of metacarpals. 



Fig. 2. Merychippus insignis? Leidy. No. 1377. Front view of metacarpals. 



