404 SCOTT. 



EXPLANATION OF THE PLATES. 

 (Where not otherwise indicated, all the figures are of natural size.) 



Plate XXII. 



Fig. i. Mesohippus Bairdi. Skull, from the side. X %• This skull is drawn 

 from a specimen in the Princeton Museum, with details added from specimens in the 

 Academy of Natural Sciences, Philadelphia. C. canines; Ty. tympanic bulla; par- 

 paroccipital process; Ms. mastoid portion of the periotic. 



Fig. 2. Mesohippus Bairdi. Skull, base view of a somewhat larger specimen. 

 X |£- i.f. incisive foramen; c. canine alveolus; m. i, first molar; ac. alisphenoid 

 canal; Ty. tympanic bulla; par. paroccipital process; c.f. condylar foramen. 



Fig. 3. Mesohippus Bairdi. Atlas, dorsal view. Cope collection, v. c. verte- 

 brarterial canal; a. n. atlanteal notch. 



Fig. 4. Equus caballus. Atlas, ventral view. X /4- After de Blainville. 



Fig. 5. Mesohippus Bairdi. Axis, from the side. 



Fig. 6. " " Axis, postzygapophyses seen from above. 



Fig. 7. " " The same, another specimen. 



Fig. 8. " " Axis, seen from the front. 



Fig. 9. " " The same, another specimen. 



Fig. 10. " " Fifth cervical vertebra, from the side. 



Fig. 11. " " Sixth cervical vertebra, from the front. 



Fig. 12. " " The same, from the side. 



Fig. 13. " " Second dorsal vertebra, from the side. 



Fig. 14. " " The same, from the front. 



Fig. 15. " " Last dorsal vertebra, from the side. Cope col- 



lection. 



Fig. 16. " " Last lumbar vertebra, from behind. 



\ 



