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BULLETIN 43, UNITED STATES NATIONAL MUSEUM. 



I. The Bat, in which the humerus is long and slender, with a small pectoral 

 ridge. Ulna rudimentary. The radius constitutes the hulk of the forearm ; 

 carpus composed of six hones ; the metacarpal hones, five in numher, sepa- 

 rate and distinct ; the phalanges generally, two in number ; thumb, and in 

 some genera the index finger, surmounted by a claw. 

 II. The Pterodactyl, in which the humerus is short and straight, very broad 

 at head, with angular and prominent pectoral ridge; ulna and radius dis- 

 tinct, of nearly equal size; carpus composed of five bones; metacarpus of 

 four houcs, separate and distinct; first finger with three joints, second 

 with four, third with five, fourth with four joints, all provided with claws, 

 with the exception of the fourth, which is remarkable for the extraordinary 

 development of its several joints. It is from this last-mentioned finger to 

 the base of the foot that the skin Avas stretched by which the animal was 

 enabled to fly. 



c ^ ^:^^^ D 



DIAGRAM OF THE liONES OF ANTERIOll EXTREMITIES OF FLYING VERTEBRATES. 



A. Bat.— a. Scapula, b. Humerus, c. Kadins. d. Eudinieut of ulna anchylospd to radius, e. Car- 



pus. /. Metacarpus, g. Phalanges. 



B. ARCH.EOPTERYX. — Kefereuces as in Fig. 1. The dotted outlines seen at carpus and the terminal 



phalanges are restored portions. 



C. Bird. References as in Fig. 1. The dotted outline of the second ungual phalanx indicates the 



occasional occurrence of a claw at this point. The majority of birds are without it. 



D. Pterodactyle. — References the same as in Fig. 1 



