700 5. W. WILLISTON 



In all these forms it will be observed that the fifth digit is much 

 reduced, more so than in the hind feet of the same animals. The 

 number of phalanges in this finger in each is three and no more ; this 

 is positive. Furthermore it will also be observed that the support- 

 ing carpale 5 is reduced or wanting in all; that is, the loss of this 

 bone, the rule in all later reptiles, had begun even before the close 

 of Carboniferous times. 1 



It may therefore be assumed with assurance that the ancestors 

 of the pterosaurs had the phalangeal formula for the hand of 2, 3, 

 4, 5, 3, with the fifth finger much reduced in size and its supporting 

 carpale 5 greatly reduced or entirely lost. In adaptation to aerial 

 flight the pectoral girdle 2 and front limbs in the pterodactyls have 

 been greatly modified throughout. In Pteranodon and Nyctosaurus, 

 the most highly specialized, but three carpal bones remain, a 

 proximal one, doubtless the fused radiale, intermedium, and ulnare; 

 a lateral carpal for the support of the pteroid, which may be either 

 the centrale or the first carpale; and a distal one, which in my 

 opinion represents the fourth carpale alone; which, it will be seen, 

 is the largest in reptiles. The carpale bearing the "Flugfinger" is 

 always the larger; in Pterodactylus there is another, smaller one 

 in front bearing the anterior metacarpals. I cannot believe that 

 this carpale is the reduced or lost fifth carpale of the ancestral 

 pterosaur carpus, nor that the wing-finger has migrated from its 

 own vestigial carpale to the enlarged fourth while the fourth has 

 migrated to a more anterior carpale. From the carpus then of 

 pterodactyls it would seem highly probable that the carpale is the 

 fourth and that it supports its proper finger the fourth, and not 

 the fifth. 



As has been known since the time of Cuvier, the phalangeal 

 formula in pterodactyls, beginning with the first clawed finger, is 



1 1 may mention here that evidence is accumulating to prove that the so-called 

 Permian of Texas, or at least its lower part, and of New Mexico, as well as of Illinois, 

 really pertains to the upper part of the Pennsylvanian. 



2 In my recent work on American Permian Vertebrates, p. 58, fourth line from 

 bottom, occurs an unfortunate error, due to the omission of a qualifying phrase, 

 "absent 'among nonamphibious reptiles,'" whereby I say that the supracoracoid 

 foramen is wanting only among Pterosauria, when its absence in the Plesiosauria, most 

 Ichthyosauria, Phytosauria, Chelonia is known to all. 



