THE MAMMALIA OF THE DEEP IUVER BEDS. 89 



tion of the bone in the middle is less marked. The groove for the metacarpal carina 

 is deep near the palmar side; dorsally it becomes very faint, but is continued across 

 the entire proximal surface and very slightly notches the anterior margin. On the 

 palmar side of the phalanx the triangular roughened area for the attachment of the 

 inferior sesamoid ligament, which in the horse descends nearly to the distal trochlea, 

 is in Desmatippus very much smaller and confined to the proximal portion of the 

 bone. The distal articular surface is less convex than in the horse, and is less 

 reflected upon the dorsal and palmar sides ; upon the latter side its margin is inter- 

 rupted by a notch, which, however, is not so long or so deep as in the modern genus. 

 The second phalanx is longer and more slender proportionately than in the horse, and 

 is also more depressed and flattened than in that animal ; the proximal articular sur- 

 face is less concave, its median ridge less pronounced, and the tubercles for the 

 attachment of the lateral interphalangeal ligaments are but slightly developed. The 

 distal articular surface is not reflected so far upon the dorsal side as in JEJquus, though 

 on the plantar side it rises as high relatively and the surface for the so-called navicu- 

 lar sesamoid is well marked. The ungual phalanx is only partially preserved, but 

 enough remains to show that it is more equine in character than the long, depressed 

 and flattened ungual of AncMlherium aurelianense. The line of the dorsal surface 

 descends more steeply than in that species and the front margin of the proximal 

 surface is elevated in the median line to form a slightly recurved, hook-shaped pro- 

 cess, which, though much less prominent than in the horse, is much more so than in 

 A. aurelianense. 



The lateral digits, so far as can be judged from the fragmentary remains, were 

 still fairly developed, and though much more reduced than in Midhippus, appear to 

 be somewhat less so than in Proiohippus. The distal trochlea of the metacarpal is 

 less developed in proportion to the breadth of the shaft than in the John Day forms. 



Measurements. 



M. 



Metacarpal iii, length 185 



Metacarpal iii, width of proximal end 020 



Metacarpal iii, width of distal end 018 



Metacarpal ii, width of distal end 009 



• Metacarpal ii, depth of distal end 015 



First phalanx iii digit, length 050 



First phalanx iii digit, width of proximal end 024 



" First phalanx iii digit, width of distal end 020 



Second phalanx iii digit, length 020 



Second phalanx iii digit, width of proximal end 024 



Second phalanx iii digit, width of distal end 021 



Third phalanx iii digit, width of proximal facet 022 



