Vol. 69.] SKELETON OF ORNITHODESMUS LATIDEJSTSk 397 



of the wrist prevented either inward or outward dislocation. In 

 all the forms the wing has been made to bend posteriorly from 

 the wing-metacarpal and proximal phalange-joint, but this was not 

 the case here. Dr. Plieninger 1 considers that in RTiampliorhynchus 

 Icokeni the chief articulation of the wing was less at the elbow 

 and wrist, much more between the fifth metacarpal and wing- 

 finger phalange ; and Prof. Williston ' thinks that in Orniihostoma 

 there was very ' little movement in the wrist, considerable in the 

 elbow, and very much in the shoulder.' 



It would be interesting to know whether the robust longitudinal 

 ridge (PI. XXXIX, fig. 6, ri) on the ventral surface of the ulna, 

 near the proximal end, occurs in many genera. Here, it appears, 

 the biceps-tendon was attached, and not to the radius : for there 

 is no tuberosity or cavity for its insertion apparent on the latter 

 bone, if, indeed, it were not otherwise too weak to withstand the 

 strain of flexing the lengthy limb with its patagium. 



Both extremities of the ulna and the proximal end of the wing- 

 metacarpal occupy the whole of the pre-postaxial diameters of the 

 articulations, so that the wing was carried by the humerus, ulna, 

 wing-metacarpal and phalanges, the radius only acting as a strut, 

 and the small metacarpals and phalanges giving no assistance. 

 Weak as are the small metacarpals, yet for all such purposes 

 as suspension they would be sufficiently powerful to brace the 

 manus in supporting the reptile, and their position, dorsal to the 

 ulnar metacarpal, would be an aid to the grasp. Certain it is that 

 the articulations of the wrist would permit the wing, when not 

 extended, to be not only bent backwards parallel with the body, 

 but also twisted inwards in a posterior direction, freeing it from 

 all interference with the action of the other metacarpals. Prof. 

 Williston thinks that, if Ornitlwstoma 'hung in the upright position 

 when at rest, it is difficult to see where the head was stowed 

 away ' (loc. cit.). In Ornithodesmws it would have been easy for the 

 head to be placed over or under the brachium, or drawn by the 

 retraction of the neck on to the shoulders with the skull held 

 upwards. 



The femur, with its terminal head and neck, could only be carried 

 at right angles to the long axis of the body, and its inclusion in 

 the patagium made impossible anything but a sluggish forward 

 and backward motion in ambulation. The bending of the leg to 

 reach the ground took place at the knee-joint in a lizard-like manner. 

 In recent reptiles and mammals, where the thigh is carried at 

 right angles to the body, the neck and head of the femur are 

 terminal or nearly so ; and in birds and mammals, where it takes 

 a vertical position, they are more or less at right angles. 



1 F. Plieninger, 'Die Pterosaurier der Jura Schwabens ' Palseontographica, 

 vol. liii (1907) p. 208. 



a S. W. Williston, 'Kestoration of Ornitlwstoma (Pteranodon)' Kansas Univ. 

 Quart, ser. A, vol. vi (1897) p. 38. 



