102 DINOCEKATA. 



The Scaphoid. 



(Plate XXXI, figures 1-6, Plate LIV, figure 1, s; 



and woodcuts 112-113, below.) 



The scaphoid in tlie D'mocerata is a ^^eculiar bone of characteristic 

 shape. It is quite large, its length, along the axis of the limb, being 

 greater than that of any other bone of the carpus. Proximally, it presents 

 a strongly rounded, almost hemispherical surface, for articulation witli the 

 radius. This articular face covers the entire proximal end of the bone, 

 and is oblique to its axis, the side toward the lunar being much higher 

 than the opposite side. The ulnar side, in apposition with the lunar, 

 has a proximal articular surface confluent with the radial sui-face, and 

 extending less than one-fourth the length of the bone. 



Distally, the scaphoid presents two confluent articular faces, one for 

 the trapezium, and a second smaller one, somewhat in front of the other, 

 for the trapezoid. Tliese two faces are but indistinctly separated from 

 each other, and are, for most of their extent, convex in both directions. 



The ulnar side of the bone also presents two confluent, but well 

 marked, articular surfaces, making an obtuse angle with each other. Of 

 these, the anterior is nearly flat, and joins the lunar. The })Ooterior is 

 more convex, and adapted to the magnum. This face does not reach 

 the anterior angle f)f the bone, so that the magnum is supported in front 

 by the lunar alone, Ijut articulates behind with the scaphoid also. 



The projection supporting- these two faces may perhaps represent the 

 central bone, coalesced with the scaphoid. The latter shows no face for 

 a separate central bone. 



The two proximal articular faces are well separated from the four at 

 the distal end of tlie scaphoid bone by a large area, of non-articular 

 surface. This tract becomes elevated, and strongly tuberculated, on tlie 

 exterior side of the bone, while it is smoother, and somewliat excavated, 

 on the side turned toward the lunar and the magnum. 



In Plate LIV, figure 1, the scaphoid and lunar bones are slightly out 

 of position, but every anatomist will see their true relations to each other. 



The scaphoid in Dhwceras laticeps (number 1264), like most others 

 (except number 1208), shows, near the distnl portion of the radial side, 

 below the rugose surface, a det^p a:i;l s ):new]iat oblique depression. 



