THE FOIIE FEET. 125 



The surface of the bone is roughened towards the ends, but smoother 

 along the sliaft, as shown in Plate XXXVI, figures 7 and 8, and Plate 

 XXXVII, figures 1 and 2. It is considerably extended antero-posteriorly 

 near the proximal end, but is constricted at the middle. 



The ])roximal end (Plate XXXVII, figure 3) is almost completely 

 covered by the articular face for the unciform bone, bv which the fourth 

 metacarpal was entirel}- supported. This face is convex in both 

 directions, and broad in front. It becomes much narrower behind, or 

 toward the palmar side of the manus, so as to appear triangular, but does 

 not come quite to a point. Along each side, it is confluent with narrow 

 faces, nearly at right angles with the main surface, which joined, during 

 life, corresponding faces on the third and fifth metacarpals. 



The largest of these lateral faces, shown in Plate XXXVI, fig-ure 8, 

 extends along the entire margin of the uncifoi-m face on its radial side, 

 and was adapted to the third metacarpal. 



On the opposite, or ulnar, side (Plate XXXVII, figure 2), a smaller 

 and shorter face, sometimes, as in the specimen figured, much larger 

 anteriorl)^, was adapted, during life, to the fifth metacarpal. 



The distal end of the bone (Plate XXXVI, figure 9) presents a 

 rounded, and but slightly convex, face for the phalanx, and below are 

 shallow grooves for the two sesamoid bones. 



Measurements of the fourth metacarpal bone in four specimens of 

 the Dinocerata are as follows : 



3Ieasurements of Fourth Metacarpal. (Dinoceras ?nirabile, No. 1211.) 



m. 



Total length of f ourtb metacarpal, .131 



Diameters of proximal end, .0.50-.n81 



Diameters of distal end, 052-044 



Diameters of shaft (approximate), _ - 0-38-. 041 



Antero-posterior diameter of face for unciform, .076 



Transverse diameters of face for unciform, .022-.048 



Antero-posterior diameter of face for third metacarpal, 062 



Transverse diameters of face for third metacarpal, .013-.022 



Antero-posterior diameter of face for fifth metacarpal, ._ .052 



Transverse diameters of face for fifth metacarpal, .060-.022 



Diameters of face for phalanx,-^^ — . .-- .()35-.040 



