THE FORE FEET. 



105 



l^yramidal is shown in fig-ure 10. Two narrow and approximate faces 

 are seen on this surface, becoming someAvhat Avider, and approaching each 

 other l)ehind. These faces vary greatly in the degree to wliich they are 

 devehiped in different specimens. 



The upper, or proximal, surface is confluent with the ulnar fticet, 

 while the lower, or distal, one is continuous with the face for the 

 uncifiirm, liut usually well distinguished from it b}- a ridge. 



The proximal surface (figure 11), articulating with the radius, is 

 more or less quadrangular in outline, broader in front, sometimes so 

 much so as to become sub-triangular in outline (number 1218). It is 

 well rounded in both directions throughout, the smooth articular face 

 for radius and ulna being carried over on each side to join both the 

 scaphoid and the pyramidal fj'.ces. 



Fig. 114. 



i>i ' 





FiGCHE 114. — Riglit lunar of Dhwceras mnabile, Jhirsli (Xo. 12J0); front view. 

 FlGtjuE 115. — Left lunar of Tiuoceras ingens, Marsh (No. 1504); bottom Tiew. 

 Figure 116. — Left lunar of Tinoceras ingens (No. 1219) ; front view. 



m. face for magnum ; ]). face for pyramidal ; r. face for radius ; s. face for scaphoid ; tr. face for trapezoid ; 



wn. face for unciform. 



.\11 the figures are one-half natural size. 



The distal surface (figure 12) is divided into two articular faces, 



supporting in part the magnum and the unciform. Tliese faces are 



confluent, and sometimes hardly to be distinguished in front, Init, on the 



posterior part of the surface, they are separated by a more or less distinct 



rounded ridge. Both these faces are nearly flat transversely in front, and 



somewhat concave behind. In an antero-posterior direction, they are 



convex in front, and concave l)ehind. 

 U 



