302 On the Skeleton of jSTyctodactylus, with Eestoration 



either in the shoulder joint or elsewhere. This, it will be seen, must 

 have detracted not a little from the ability to control the direction of 

 flight by the wings, while giving greater strength to them as parachutes. 

 The wing memhranes could never have have assumed any form, except 

 that of an approximate plane when distended, bellied out, perhaps, like 

 the sail of a yacht antero-posteriorly. The Joints of the wing are all 

 ginglymoidal, unless indeed a slight lateral flexibility was possible at 

 the closely united compact wrist, which is doul)tful; nor could the an- 

 terior or radial curvature of the phalanges be much, if any, greater 

 than I have indicated in the restoration. Because of this lack of rotary 

 power of the anterior extremity, I doubt not that the caudal mem- 

 branous expansion in EJiamphorltynchus served as a compensatory steer- 

 ing organ, and the same function was subserved, in a somewhat different 

 way, by the legs in the short-tailed forms. But there are much better 

 reasons for supposing that the wing membranes continued to the legs 

 or ankles of these animals. The jieculiar structure and evident j)osition 

 of the legs would have been inexplicable under any other assumption, 

 hut if the membrane was restricted to the sides of the body the patagial 

 surface must have been a mere ribbon, five or six inches wide and 

 nearly four feet long, scarcely serviceable as a wing or parachute even! 



If the animals stood erect when upon the ground, with the knees 

 rotated outward and the tibiie parallel, the wings, drooped at the side, 

 which may have been possible, would have reached the surface at the 

 metacarpophalangeal joint, with the phalanges trailing or partly folded; 

 and it is possible that in such a position, partly stooping, partly creeping, 

 the creature might have laboriously got about on land. But I do not 

 think that they often voluntarily sought the ground for ambulation. 

 Their home was in the air, and they rested suspended by the flexible, 

 sharply-clawed middle fingers. The elongated zygapophyses of the first 

 dorsal vertebra, a functional cervical, though structurally a dorsal, indi- 

 cate, not a marked backward curvature of the neck at this place, but 

 rather the possibility of a marked anterior curvature. Perhaps the neck 

 was sufficiently flexible to permit a strong sigmoid curvature, bringing 

 the head in a forward direction when in a prone position. 



It is commonly believed that the small, slender bone articulating with 

 the wrist and directed backward toward the shoulder — the so-called 

 pteroid or thumb metacarpal— was for the support of the membrane in 

 front of the elbow. 



I am satisfied that this was not its function, for the simple reason, as 

 I believe, that there was no membrane there, unless it extended on the 

 sides of the neck broadly towards the skull! This may seem a mere 



