﻿LIASSIC FORMATIONS. 



37 



occurs in the same place and with the same course in both forearms, I infer it to be 

 natural, and that the quasi-olecranon was of the nature of a sesamoid, closely articu- 

 lated with the body of the ulna. The extreme length of the ulna, from the apex of 

 this part or process (55') is 5 inches ; the greatest breadth of the ulna 3 inches. The 

 proximal articular surface joins the ulnar facet of the humerus, beyond which the 

 olecranon projects. The distal surface of the ulna articulates with the lunare (1), the 

 cuneiforme ( c ), and with an ossicle (p) wedged into the interspace posteriorly 

 between it and the ulna, which ossicle may represent the pisiforme. With the excep- 

 tion of about one third of the middle of the shaft, the exposed surface of both radius 

 and ulna is roughened by coarse rugae and small tubercles. 



The carpus includes eight ossicles. The scaphoid (fig. 2, s ) is an oblong bone, 

 with its dimension greatest transversely, viz., 2 inches, longest at its ulnar side, which 

 is 1 inch 3 lines, with a slight angular projection at its free radial border. The lunare 

 (ib., 1) is subreniform, with the concavity, representing the " pelvis of the kidney," com- 

 pleting the lower part of the inter-osseous space, for the radius and ulna are separate 

 below as well as above, and for a greater extent, the radius extending for nearly an inch 

 below or beyond the ulna. The rest of the circumference of the lunare is divided more 

 or less distinctly into its articular surfaces for the radius, scaphoides Q, trapezoides [ g ), 

 magnum (m), cuneiforme (c), and ulna. The ulnar surface has a sigmoid form. The 

 lunare (/) is larger than the scaphoid. The cuneiforme (c), about the size of the lunare, 

 has a subhexagonal shape ; the two proximal sides articulate with the ulna and pisi- 

 forme (p), the radial side with the lunare, the ulnar side with the unciforme ( M ), the 

 two distal sides with the magnum (m), and the base of the fifth metacarpal ( v ), which, 

 as in some other Plesiosauri, ascends above the rest to this connection, severing, so to 

 speak, the unciforme ( M ) from the magnum (»«). The pisiforme { p ) is a subtriangular 

 small bone, wedged into the outer interspace between the ulna and cuneiforme. In the 

 distal row of carpals the trapezium (t) is subquadrate, broader toward the scaphoid, 

 narrower where it supports the first metacarpal (1) ; it is about half the size of the 

 scaphoid. The trapezoides (g) is also subquadrate, but of larger size, articulating with 

 the scaphoid, trapezium, the ulnar angle of the base of the first metacarpal, wholly 

 sustaining the second metacarpal, articulating with the radial side of the base of the 

 third metacarpal, with the os magnum ( m ), and with the lunare (/). The os magnum ( m ), 

 of similar size, is hexagonal ; the two proximal surfaces articulate with the lunare and 

 cuneiforme, entering the angle which they leave ; the two distal surfaces articulate 

 with the third and fourth metacarpals ; the radial side with the trapezoides, the ulnar 

 side with the corresponding part of the base of the fifth metacarpal ; the displaced 

 outermost bone of the distal row is limited to its articulation with the ulnar border of 

 the cuneiforme (c) ; it is the smallest of the carpal series. 



The bones of the digits are small in comparison with those of the carpus and fore- 

 arm. The entire breadth of the carpus being 6 inches 5 lines, that of the middle of 



