386 MR. R. W. HOOLEY ON THE [June I913,- 



quite different from those of the other genera where the distal end 

 is more or less obtuse. The ulnar crest is moderately developed. 

 Between the deltoid and ulnar crests the ventral surface of the 

 bone is concave, but becomes convex as soon as the radial crest is 

 passed. The shaft gradually decreases in size until, in the median 

 region, it has a diameter of 22 mm. ; from here it rapidly expands 

 to the extremity, where its pre-postaxial diameter is 64 mm. 

 The bone here is triangular, the apex being on the median line of 

 the dorsal surface. Immediately underlying the apex on the- 

 articulation there is a large circular opening into the shaft 

 (PL XXXIX, fig. 3, /.). A. similar vacuity is found in many of 

 the humeri included in the genus Ornithocheirus of the Cambridge 

 Greensand. On the preaxial side of this opening is a small, feebly- 

 convex, triangular surface, on which the preaxial moiety of the- 

 proximal end of the ulna articulated. Yentral to it is a mode- 

 rately developed trochlear joint, oblique, looking outwards, and 

 forming the articulation for the radius (PI. XXXIX, fig. 3. tr.) 

 On the postaxial side of the central opening is a deep valley (v.), 

 which traverses the ulnar condyle diagonally, from the ulnar 

 tubercle to the central pit. The ulnar tubercle is produced distally ; 

 it is strong and claw-like, with a concave side facing the articula- 

 tion. Two strong ridges border the valley, the tipper of which 

 rises vertically from the bottom of the valley, while the lower 

 has a sloping face. The dorsal border of the distal end over the 

 upper ridge is much compressed, buttressing the ridge, and making- 

 it appear as if the edge of the bone had been doubled over. The 

 distal articular extremity is beautifully preserved in the Atherfield 

 specimen Xo. 1 (PI. XXXIX, fig. 3)« and the proximal ends of 

 the radius and ulna (PI. XXXIX, fig. 4) are in a like condition. 

 The median area of the dorsal surface at the distal end is much 

 inflated, and slightly concave at the pre-postaxial borders. A very- 

 strong epiphysis (PI. XXXIX, fig. 2, ep.) overlapping the bone is- 

 present on the preaxial border of the ventral surface. It formed 

 a support to what must have been a very large tendon, which was 

 inserted in a deep cavity under the inner condyle of the trochlear 

 joint for the radius. This pit is separated by a broad convex 

 ridge from another, situated near, but postaxial to, the median line 

 of the bone. A large pneumatic foramen is present in this cavity.. 

 On the postaxial border of the ventral surface, and nearer the- 

 distal end than the one on the preaxial, is a ridge (PI. XXXIX, 

 fig. 2, rL), the distal termination of which does not follow the 

 border, but passes inwards on to the ventral surface. The ridges 

 and valleys of the distal ventral surface give a sigmoid outline, 

 proximally to which the bone becomes convex. The postaxial 

 border of the distal end is remarkably robust, and produced 

 outwards from the long axis of the bone ; while the preaxial is 

 parallel to it. A restoration of the right humerus is given im 

 PI. XXXIX, fig. 2. 



