6 PROFESSOR OWEN ON THE GENUS DINORNIS. 
inner surface sloping rather more than the outer one: this character distinguishes the 
phalanx in question from the corresponding one in the other toes (111. 2 or 1v. 2). The 
under surface is flattened, the upper one slightly concave lengthwise. The distal 
trochlea, divided by the vertical wide groove, is more contracted above than in 11. 1. 
The pits for the lateral ligaments are large and well-marked ; that on the outer side is 
the deepest and has a tuberosity beneath it. 
The third or ungual phalanx (11. 3) is three inches in length; it is figured some- 
what foreshortened, being viewed as it is naturally bent in Pl. I. It is a sub- 
triedral long cone, bent slightly downwards. The proximal articular surface is 
shield-shaped with the base downwards; it is nearly equally divided by the vertical 
ridge which fits into the groove of 11. 2: the under surface of the base of the phalanx 
presents a broad rough surface for the insertion of the flexor perforans tendon ; the rest 
of the under surface is smooth and nearly flat transversely, slightly curved lengthwise. 
The lateral surfaces converge to an upper smooth convexity, which near the base of the 
phalanx shows the line of insertion of the expanded extensor tendon. The inner surface 
is most sloping and most extensive: the upper surface is smooth and convex ; each side 
is impressed by a deep vascular groove extending half way towards the apex of the 
phalanx. The apex of the claw is pierced by many large vascular canals, for the issue 
of the vessels supplying the secreting organ of the powerful claw. 
The length of the toe 11, as given by the three phalanges, is seven inches and a half. 
The length of the proximal phalanx of the middle toe (111. 1) is four inches and a half; 
the form of its proximal articular surface is shown at fig. 3, 11.1. A rough, somewhat 
prominent tract, of a triangular shape, extends from the lower angles of the proximal 
surface forwards upon the lateral and under surface of the shaft, over more than one- 
third of its extent ; and they bound a shallow channel which impresses the middle of 
the under surface of that part of the bone. The section of the middle of the shaft of 
this phalanx yields a full transverse ellipse, a little flattened at the under part. The 
upper surface of the phalanx is almost straight lengthwise: there is a slight depression 
above the upper border of the distal trochlea. This trochlea is more equally divided, 
and by a less deep median groove, into the two articular convexities, than in the pha- 
lanx 11. 1: there is a depression at the middle of the under border of the surface, and 
a deep and large ligamentous depression on each side of the distal trochlea. The 
second phalanx, ir. 2, differs from 11. 2, not only by its greater size, but by its more 
symmetrical form, and by the straight line in which the upper surface extends from 
the posterior to the anterior trochlea. The inner of the two divisions of the proximal 
trochlea is rather the largest, but the inequality is less thanin 11.2. The distal trochlea 
is almost symmetrical; the under surface is more deeply notched than in 1. 2: the 
outer of the two impressions for the lateral ligament is the deepest. 
The third phalanx, 111. 3, has almost a square contour, with three of the sides slightly 
concave, and the fourth formed by the proximal articular surface slightly produced at 
