110 THE MAMMALIA OF THE DEEP RIVER BEDS. 



ference from the American species in the ischiadic or supra-acetabular crest, which 

 is more rounded and thickened even than in the horses. Both species agree in hav- 

 ing a sulcus for the tendon of the internal obturator muscle. 



The only other part of the hind limb of A. equinum which is known consists of 

 some fragments of the distal ends of the metatarsals and phalanges of another speci- 

 men. These are larger than the corresponding parts of the manus, but otherwise 

 like them. 



The type specimen of A. equinum was found by Mr. I. Benet in the upper beds 

 of Deep river (lower Loup Fork), Mont. 



Measurements. 



A. EQUINUM. A. AURELIANENSE. 



M. M. 



Humerus, length 224 .230 



Humerus, width of proximal end 066 .063 



Humerus, depth of proximal end 072 .075 



Humerus, width of distal trochlea 053 .049 



Radius, length 265 .250 



Radius, width of humeral trochlea 051 .050 



Radius, width between inferior tuberosities 050 .060 



Radius, width of shaft in the middle .030 



Radius, depth of shaft in the middle .019 



Radius, depth of humeral surface 026 .025 



Radius, width of facets for the ulna 031 .040 



Scaphoid, width of proximal end 019 .017 



Scaphoid, width at middle 016 .014 



Scaphoid, width of distal end 018 .015 



Scaphoid, height of anterior face 021 .023 



Lunar, width of distal end 018 .017 



Lunar, width of unciform facet 007 .005 



Lunar, height of anterior face 022 .... 



Cuneiform, height 016 .... 



Cuneiform, depth of distal end 023 



Trapezoid, height 012 



Trapezoid, width 011 .... 



Magnum, anterior height 015 .013 



Magnum, anterior width 030 " .025 



Magnum, posterior width 010 .007 



Magnum, posterior height 018 .021 



Magnum, depth 026 .026 



Pisiform, length 033 



Pisiform, height of proximal end 011 .... 



Metacarpal iii, length 194 .196 



Metacarpal iii, width of proximal end 028 .030 



Metacarpal iii, width in the middle 023 .024 



Metacarpal iii, width of distal end 028 .028 



