348 



Transactions. — Geology. 



giving it more the look of a cetacean than a reptilian limb-bone. The distal 

 extremity is flattened at right angles to the greatest expansion of the proximal, 

 and has two distinct, slightly concave, articular surfaces to receive the ulna 

 and radius. The plantar surface is smooth and slightly concave. The palmar 

 surface slightly convex, and has a bold, rugose tuberosity in the middle to 

 receive the attachment of the bicipital tendon, indicating powerful rotatory 

 movements of the limb. 



Dimensions. 







Inches. 



Length 



... 11-5 



Diameter — articular surface 





.. 5 



Diameter — neck 





,. 4 



Length — trochanteroid surface 





.. 4-5 



Width 





.. 2-5 



Width — middle of bone ... 





.. 4-5 



Thickness 





.. 2-5 



Width- — distal extremity .. . 





.. 9 



Thickness 





.. 2-5 



Radius. — A pentagonal bone, with thin external margin and convex 

 articular surfaces, and with a notch on the surface in contact with the ulna. 

 It has two carpal articu.lations. 



Length 

 Width 



Inches. 



3 



2-8 



Ulna. — A hexagonal bone, with convex articulation. 



Inches. 



Length ... ... ... ... ... 3-5 



Width ... ... ... ... ... 4 



Garpals. — The radial is cuneiform, with thi'ee ax-ticular sui'faces and a 

 bevelled external. 



Inches. 



Length ' ... ... ... ... ... 2 



Width ... ... ... ... ... 3 



The intermedium is pentagonal. 



Inches. 



2-5 

 2-5 



Length 

 Width 



Ulnar e is hexagonal, with five articular surfaces. 



Distal Carpals. — 1st has four articular surfaces, is rounded, and channelled 



extern ally I 



Inches. 



1-5 



•2-5 



Length 

 Width 



It articulates with two phalanges. 



2nd also articulates with two phalanges, having, in all, five articular 

 surfaces. 



3rd is also pentagonal; articulates with only one phalange and the idnare; 

 the other surfaces not having perfect articulations. 



