No. 2.] THE RELATIONS OF PROTOCERAS. 343 



metacarpus might with almost equal propriety be called either 

 "unreduced" or " inadaptive," to use Kowalevsky's terms, 

 because this manus is not reduced farther than is involved in 

 the loss of the pollex and enlargement of the median digits. 

 As Osborn and Wortman have suggested, a rudimentary first 

 metacarpal may have been present. This suggestion is made 

 more probable by the fact that the proximal end of metacarpal 

 II has its internal angle truncated and slightly hollowed for the 

 space of about half an inch, as if for the reception of a short 

 splint-bone. This surface is much too large to have been 

 occupied entirely by the trapezium, and nothing of the kind is 

 apparent on mc. V. 



The second metacarpal has a narrow, triangular head, with a 

 plane surface for the trapezoid, and on the ulnar side a minute 

 facet for the magnum, which is oblique and rises above the top 

 of mc. III. The small size of this facet as compared with the 

 same in such a genus as Ancodtts, for example, is an indication 

 that the connection of the magnum with mc. II was undergoing 

 reduction. The shaft is slender, compressed, strongly curved, 

 and of trihedral section, the apex of the triangle being at the 

 contact with mc. III. The distal end is slightly thickened and 

 expanded, but the trochlea is narrow and rounded. 



The third metacarpal is the longest of the series, extending 

 both above and below mc. IV, as is also the case in Oreodon 

 and Ancodus. The head is but little expanded, the longest 

 diameter being the dorso-palmar one, and the head not being 

 extended toward the radial side, as it is in Gelocus, in which 

 mc. Ill covers nearly or quite all the distal surface of the 

 coossified magnum and trapezoid. The proximal surface is 

 taken up by the large, slightly saddle-shaped facet for the 

 magnum, while a stout, oblique process overlaps the head of 

 mc. IV, and abuts against the unciform ; this unciform process 

 is longer and more prominent than in Gelocus. There is no 

 facet for the trapezoid, mc. Ill being cut off from that bone 

 by the connection of mc. II with the magnum. On the palmar 

 side of the head is a small circular facet, which projects strongly 

 toward the ulnar side and articulates with a corresponding 

 facet on mc. IV. The shaft is of nearly uniform diameter 



