10 FOSSIL REPTILIA OF THE 



of the phalanx, upon the palmar surface of the shaft, two thirds across. All the rest of 

 that surface is grooved and roughened for ligamentous attachment. 



The distal end of this phalanx is 2 inches in breadth ; of this, a feebly convex, semi- 

 oval articular surface occupies a transverse extent of 1 inch 5 lines ; the breadth from the 

 anconal to the thenal border of this surface gives that of the distal end of the phalanx, 

 viz. 1 inch. 



The series of bones does not include any phalanx adapted to or agreeing in size with 

 this surface. By the analogy of Sauria and Crocodiiia, I conclude the missing phalanx 

 would be the terminal one. Of the proximal phalanx of the ' pollex,' Mr. Beckles' series 

 includes both right and left. 



The second metacarpal (PI. Ill, 2, m), or that of the index digit, is 6 inches in 

 length. The proximal end is subquadrate, 2 inches in breadth, deviating from flatness 

 by a slight convexity, most marked towards the ulnar side, where it probably projected 

 into the cleft between the trapezoides and os magnum. 



There is no indication of a smooth synovial surface ; the union throughout, or nearly 

 so, seems to have been ligamentous ; the longest diameter in the ancono-thenal direction 

 is toward the ulnar side of the surface, and is 1 inch 8 lines. 



Near the radial side of the base is a rough surface of limited extent, apparently for 

 ligamentous connection with the adapted surface of the first metacarpal. 



On the ulnar side of the second metacarpal a rough flattened tract projects, like an 

 exostosis, from the whole length of that side of the bone. Its ancono-thenal breadth at 

 the base of the metacarpal is 1 inch 6 lines ; it decreases to a breadth of 6 lines where it 

 passes into the rough surface for the lateral ligament on the ulnar side of the distal end. 



The anconal surface of the shaft is smooth, becoming roughened by linear stria? as it 

 bends upon the radial surface. The thenal surface of the shaft is ridged and grooved 

 throughout ; it is nearly flat transversely, moderately concave lengthwise. The distal 

 articular surface is moderately convex, 1 inch 4 lines in diameter ; there is a protuberance 

 on each side of the thenal part of the distal end ; the ulnar side of the bone is slightly 

 convex ; the radial one in a greater degree concave ; thus, the second metacarpal is slightly 

 bent toward the radial side of the paw. 



The bone described belongs to the left foot. The proximal part of the same phalanx 

 of the right foot is preserved. 



The proximal phalanx of the second toe (ib., n, 1) is 2 inches 6 lines in length ; 2 

 inches in breadth at the proximal end; 1 inch 9 lines at the distal end. The proximal 

 articular surface has the smooth synovial character but slightly indicated. It is subcircular 

 in form, about an inch in diameter, with a very feeble concavity ; the rough peripheral tract 

 on nearly the same plane, from 4 to 6 lines in breadth, indicates how large a proportion 

 of the joint had been syndesmotic : the protuberance for the lateral ligament on the radial 

 side projects beyond the plane of the articulation ; that on the ulnar side has a more distal 

 relation to the joint. The anconal and lateral surfaces of the shaft form a continuous 



