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 (iii. 2 or iv. 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 ii. 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 (ii. 3) is three inches in length ; it is figured some- 

 what foreshortened, being viewed as it is naturally bent in PI. 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 ii. 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 ii, as given by the three phalanges, is seven inches and a half. 

 The length of the proximal phalanx of the middle toe (iii. 1) is four inches and a half; 

 the form of its proximal articular surface is shown at fig. 3, iii. 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 II. 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, iii. 2, differs from ii. 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 than in ii. 2. The distal trochlea 

 is almost symmetrical ; the under surface is more deeply notched than in ii. 2 : the 

 outer of the two impressions for the lateral ligament is the deepest. 



The third phalanx, in. 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 



