104 DINOCERATA. 



The Lunar. 



(Plate XXXI, figures 7-12, Plate LIV, figure 1, I; and 



woodcuts 114-116, below.) 



The lunar bone in the Dinocerata (Plate XXXI, figures 7-12) bears 

 some resemblance to the corresponding bone in the elephant, but differs 

 widely from it in having its proximal surface, for articulation with the 

 radius and ulna, convex throughout, instead of being- for the most part 

 concave. The distal surface, also, presents two distinct articular faces, 

 instead of being covered with a single large face, as in the elephant. 



The exterior surface of the lunar, or the face seen in front ^\■hen 

 the bone is in its natural position with the other bones of the foot, 

 is represented on Plate XXXI, figure 7. This surface is coarsely 

 roughened, and is widest above. Only a small portion of the edges of 

 any of the articular surfaces can be seen in this view. 



The inner angle of the distal end of the lunar in I)ii/oceras (numbers 

 1215, 1229, and 1230) is truncated by a small face i'vv articulation with 

 the trapezoid bone, as shown in figure 7, and also in woodcut 114, below. 

 On one specimen (number 1575), wliich may belong to UintatJierhini, this 

 face is hirge and convex. In number 1254, the fiice is smaller than in 

 the specimens figured. The articulation of the lunar with the trapezoid, 

 or perhaps the trapezo-central bone, occurs also in CorypJiodon, Mastodon, 

 and the elephant, especially the African species. 



The lateral surface of the bone turned toward the scaphoid, and 

 articulating with it, is shown on Plate XXXI, figure 8. This side has two 

 faces for articulation with the scaphoid. The upper one of these runs 

 along nearly the whole extent of the superior margin of the bone, and is 

 confluent with the surface for articulation with the radius, and hardly to be 

 distinguished from it. A second articular face for union with the scaphoid 

 is broader and more flattened than the first, and extends along rather 

 more than half of the distal margin near its front, or anterior, end. Behind 

 this articular surface, the bone is produced into a short, hook-shaped 

 process sustaining the concave portion of the distal articulations. 



The posterior surface of the lunar is shown on the same Plate, figure 

 'J, and presents no articular faces. 'i'lie lateral surface turned toward the 



