'390 J[R. E. W. HOOLEY OX THE [Julie I913, 



convexity on the distal end of the ulna (PI. XXXIX, fig. 7, B), 

 and the raised surface of the concave postaxial surface of the 

 articulation (PI. XXXIX, fig. 8, C) articulates with the circular 

 facet on the ventral surface near the postaxial border of the ulna 

 (PI. XXXIX, fig. 6, fa.) ; while the rest of the concavity articu- 

 lates with the convexity on the postaxial extremity of the ulna. 

 The distal articulation of the proximal carpal, and the proximal of 

 the distal carpal cannot be seen, as the bones are cemented together 

 by matrix ; yet, so close are they in all perceptible characters to 

 some of those from tbe Cambridge Greensand, that no doubt can 

 be entertained as to the similarity of their articulations. 



The distal articulation of the proximal carpal, as seen in the 

 ■ Cambridge specimens, comprises two transverse concave surfaces 

 divided by a ridge, the dorsal one being only half the extent of the 

 ventral. The smaller is oblique, looking outwards, and the larger 

 distally ; but, as it terminates at the distal end of the wedge-like 

 prolongation on the postaxial edge of this carpal, it becomes raised 

 here, and also looks outwards. 



The proximal articular surface of the distal carpal has con- 

 vexities corresponding to the concave surfaces of the distal end of 

 the proximal carpal. Thus a trochlear joint is formed, Avith a pre- 

 postaxial movement. The distal articulation of the distal carpal is 

 beautifully seen in the Atherfield specimen Xo. 1. X early in 

 the centre of the articulation is a very large and deep circular pit 

 (PI. XXXIX, fig. 9, D), the diameter of which is 17 mm. Dorsally 

 to this is an elongated, narrow, shallow and concave, articular 

 surface, placed obliquely, so that it looks both upwards and 

 distally ( 0). This takes no part in the articulation with the 

 wing-metacarpal ; it is dorsal to it, and on a different plane. The 

 small metacarpals articulated here. On the preaxial side of the 

 central cavity and ventral to that just described, is a triangular 

 area, the ventral angle of which is continued round the central 

 pit; ventrally to this the bone expands, and then narrows and 

 extends as a curved bar to the articulation for the small meta- 

 carpals, and thus the central cavity is completely bounded. All 

 these surfaces slope inwards, forming a socket (PI. XXXIX, 

 fig. 9, B) in which the main proximal end of the wing-metacarpal 

 articulated. In addition to these surfaces there is a quadrangular 

 articular facet (PI. XXXIX, fig. 9, A) below the plane of the 

 others, and more proximal, also for articulation with the wing- 

 metacarpal (PI. XXXIX, fig. 10, A) ; but, as will hereafter be 

 shown, not during flight, as that would have been impossible, and 

 to perform an entirely different function. The lateral carpal is 

 a small shovel-shaped bone, but may have approximated closely to 

 the American forms in life, as it is slightly waterworn on the side 

 on which the emargination occurs in those genera. It is longer 

 than wide, and has a depth of about half its length. It fits in 

 between, and presumably articulates with, the two elongated pro- 

 cesses thrown out, on their preaxial borders, by the proximal and 

 distal carpals. 



