ORDER IX 



PTEROSAUKIA 



249 



humerus, and are about equally developed. The number of carpal elements 

 in both rows varies considerably. The first digit of the manus is either wanting 

 or represented by a backwardly directed styliform bone. The second, third, 

 and fourth metacarpals are closely apposed and nearly uniform in size, but 

 the fifth is very much stouter than the rest, and bears a series of four enor- 

 mously elongated phalanges, turned backward to support the wing-membrane. 

 Sometimes metacarpals, Nos. ii to iv are incomplete, and either filiform or 

 tapering to a point proximally, being fixed only to the side of the greatly 



Fig. 353. 



RhamphorhyncJms phyllurus, Marsh. Upper Jura (Lithographie Stoiie) ; Bavaria. Restoration, 



showing extent of cutaneous expansions, 1/7 (froiii A. S. Woodward, after Marsh). 



developed metacarpal of the wing-digit. The three inner digits are clawed 

 and exhibit the phalangeal formula 2, 3, 4. They are entirely free from the 

 membranous expansion of the fifth digit (Fig. 353). Attached to the radial 

 side of the carpus is sometimes observed a slender splint-like bone, which is 

 directed backward nearly parallel with the radius and ulna. This is the so-called 



Fig. 354. 



Rhamphorhynchus gemmingi, v. Meyer. Ui)per Jura (Litliographic 

 Stone); Bichstadt, Bavaria. Right fore-linib with impression of volant 

 niembrane. 



" pteroid bone " (SpannJcnochen, von Meyer), which some writers have regarded 

 as an ossified tendon, or as a support for the wing membrane ; but it is more 

 properly interpreted as a rudimentary, abnormally reflexed first metacarpal. 

 The cutaneous expansion, or patagium (Fig. 354), is quite narrow and tapering, 

 in this respect resembling the wing of a swallow or sea-gull. It was attached 

 at its base along the sides of the body wall, and extended beyond the bind 

 limbs to the base of the tail. In at least one genus {Rhamphorhynchis) it also 

 developed a leaf-like expansion at the extremity of the tail (Fig. 353). The 



