406 SCOTT. 



Plate XXIII. 



FlG. 17. Mesohippus Bairdi. Skull, longitudinal section. 0. c. occipital condyle ; 

 B. S. basi-sphenoid (crushed out of place); Cb. F. cerebellar fossa; C. F. cerebral 

 fossa; F. S. frontal sinus. 



Fig. 18. Equus caballus. Skull, longitudinal section. X %. After de Blainville. 



Fig. 19. Mesohippus Bairdi. Left humerus, from the front. X %. e. t. exter- 

 nal tuberosity; i.t. internal tuberosity; beg. bicipital groove; d. r. deltoid ridge. 



Fig. 20. The same, from the outer side. X %. 



Fig. 21. The same, proximal end. 



Fig. 22. The same, distal end. 



Fig. 23. Mesohippus Bairdi. Left ulna and radius, from the outer side. R. 

 radius; U. ulna. 



Fig. 24. Mesohippus Bairdi. Radius, proximal end, from the front. 



Fig. 25. " " Radius, distal end. s', scaphoidal facet; /', lunar 



facet. 



Fig. 26. Mesohippus Bairdi. Right manus, from the front. S. scaphoid; L. 

 lunar; C. cuneiform; Tin. trapezium; M. magnum; U. unciform. 



Fig. 27. Mesohippus Bairdi. The same, from the outer side. 



Fig. 28. " " The same, proximal view. 



FlG. 29. Equus caballus. Carpus, from the front. Y.%. After de Blainville. 



Fig. 30. Mesohippus Bairdi. Metacarpals II., III., and IV., proximal ends. 



FlG. 31. Mesohippus Bairdi. Right innominate bone, from the side. X %• 

 t. i. tuberosity of the ischium. (Cope collection.) 



Fig. 32. Mesohippus Bairdi. Left tibia, from the front. T. tibia; F. fibula. 

 X%. 



Fig. ^2' Mesohippus Bairdi. The same, distal end. 



Fig. 34. " " Left tarsus, from the front, cf. fibular facet of 



calcaneum; Cb. cuboid; N. navicular; C. s ecto-cuneiform; C. 1 + 2, coalesced 

 meso- and ento-cuneiforms. 



Fig. 35. Equus caballus. Right tarsus, from the front. X %■ After de Blain- 

 ville. 



Fig. 36. Mesohippus Bairdi. Left tarsus, distal end. 



Fig. 37. " " Left astragalus, plantar side, c', c", <-"', facets 



for the calcaneum; cb. for the cuboid. 



Fig. 38. Mesohippus Bairdi. Left calcaneum, from the medial side, a', a", a'", 

 facets for the astragalus; cf. for the fibula. 



Fig. 39. Mesohippus Bairdi. Right metatarsus. X %• 



