34 ME GALON YX. 



in the middle it is convex, but between the dorsal pair of lobes is concave. The 

 lower lobe and portions of both the upper articulate with the os magnum. The 

 remaining but large portion of the inner lobe is bent forward and articulates with 

 the unciforme, whilst the remainder of the outer lobe articulates with the trapezoides. 

 From the articulation for the unciforme, a large surface (Fig. 14) extends to nearly 

 the middle of the inner side of the diaphysis, for junction with the annular meta- 

 carpal ; and from the articulation of the trapezoides, a convex, trilateral surface 

 (Fig. 2) extends upon the outer side, for junction with the index metacarpal. 



The distal extremity (Figs. 2, 6) of the bone is constructed after the same plan 

 as that of the index metacarpal, but the inner offset of the articulation is reduced 

 to a short tuberosity, which is continuous above with the^ ridge for ligamentous 

 attachment. 



Inches. 



Length obliquely 4;^ 



Breadth of shaft dorsally If 



Depth of shaft at middle . . . 1^ 



Depth of proximal extremity .2^ 



Depth of distal extremity 2^ 



The median metacarpal bone, in the collection of Jefferson, is shorter than that 

 just described, and nearly resembles it in detail, except that its distal articular pro- 

 cess possesses a well developed offset upon the inner side. 



Inches. 



Length obliquely 4 



Breadth of shaft dorsally . ■ li 



Depth of shaft at middle li 



Depth of proximal extremity . . . ' 2^ ■ 



Depth of distal extremity . . . 2^ 



The annular metacarpal bone (PL X, Figs. 6, 11), of Dr. Owen's collection, the 

 longest of the series, has a cylindroid shaft with a superficial, acute, dorsal ridge. 



The proximal extremity (Fig. 11) is bevelled off on each side, and in outline is 

 irregularly pyramidal with the apex protuberant and downward, and the base ele- 

 vated into a curved ridge. Its articular facets, which are continuous, consist of 

 a reniform surface for the auricular metacarpal, and a vertical sigmoid surface, 

 directed inwardly, for junction with the unciforme and the median metacarpal. 



The distal extremity forms a long, vertical, elliptical, articular process with an 

 offset at its outer inferior part, and a prominent marginal ridge ascending from the 

 latter, and descending almost two-thirds the length of its inner side. 



Inches. 



Length obliquely . ■ . . . . 5 



Circumference of shaft ........... 3^ 



Depth of proximal extremity 2|- 



Depth of distal extremity . 2J 



The annular metacarpal, in Col. Wailes' collection, is somewhat mutilated, but 

 it appears to have corresponded pretty closely with that above described. 



