646 GEOLOGICAL SURVEY OF THE TERRITORIES. 
The trochlea surface does not. extend inwards very far; 7%. e., does not 
pass over the end of the bone. Above it, and towards the proximal end, 
appears a distinct and prominent external condyle. 
Anconad, this extremity of the humerus presents for examination the 
upturned internal condyle and a longitudinal tendinal groove, situated 
opposite the radial convexity, with intervening indentations. ‘This ar- 
rangement lends to this aspect of the bone rather an uneven and tuber- 
ous look. The nutrient foramen, almost too minute to be observed by 
the naked eye, is found at the middle and inner aspect of the shaft. 
The radius is a long, delicate bone, with a bent and compressed shaft. 
A moderately well-expanded and circular head presents the usual con- 
cavity for the oblique tubercle of the humeral trochlea, while below is a 
feebly marked ulnar facet and bicipital tuberosity; beyond this, again, 
the shaft develops a sharp, protruding edge, that extends nearly to mid- 
shaft and into the interosseous space. 
The distal extremity of this bone is spread transversely and curved 
downwards. I¢ articulates with the upper surface and distal end of the 
ulna, and is lined above by very minute tendinal grooves. The outer 
border of this extremity presents a transverse lamina of bone that seems 
to be superadded to the dilated end. 
In articulation, the radius at first curves away from its companion, 
the ulna, to approach it again towards the carpal end, for about the outer 
third of the shaft, to remain with it until both arrive at the wrist. The 
distal border of the radius is transversely convex for an articular facette 
on the scapho-lunar. The ulna is the main bony support of the forearm, 
and, indeed, its shaft is nearly equal in size and strength to that of the 
humerus itself, having the appearance of being the true continuation of 
the pectoral limb, so diminutive and slender is the accompanying radius. 
_ Its proximal extremity is the larger, and is gently curved anconad, 
to meet the corresponding flexure of the brachium to form the elbow- 
joint, the articular surface ergaged being quite extensive and vertically 
expanded. The lower, circular, and concave trochlea is the greater sig- 
moid cavity, and is intended for the ulnar tubercle of the humerus. 
lis proximal margin is so produced as to form a strongly defined “ole- 
cranop process”, the lower lip of the cavity being the homologue of the 
“coronoid process”, and is so teebly developed as to scarcely deserve 
the distinction. In close proximity to the greater sigmoid cavity, above, 
there is another articular surface, quadrilateral in outline, decidedly 
concave from above downwards, much more shallow in the opposite di- 
rection, for the oblique tubercle. Immediately beyond its distal mar- 
gin is a weak and shallow facette for the side of the head of the radius, 
so that the oblique tubercle articulates in a cavity furnished by the 
cupped head of the radius and the larger quadrilateral trochlea of the 
cubitus, the two being almost continuous. 
The outer aspect of this extremity presents simply certain feeble ele- 
Hevens and depressions for muscles and the ligaments surrounding the 
joint. 
From the proximal extremity, the nearly cylindrical shaft curves 
gently palmad from its inner third only; after that it takes a compara- 
tively straight course for the wrist. The anconal aspect of the shaft 
presents at the junction of the inner and middle thirds an eliptical nu- 
trient foramen, that enters the bone almost perpendicularly to its long 
axis. The tubercles for the insertion of the bases of the quills of the 
secondaries, so prominent on this bone in some birds, as in Colaptes, 
seem to be entirely absent. We find them barely present in Harporhyn- 
chus, quite strongly marked in Lanius. The carpal extremity of the 
