ANATOMY OF VERTEBRATES. 177 



])halanges from the first to the fourth, and slightly increase in 

 length : each terminated by a deep compressed, curved and 

 pointed ungual phalanx. The modification converting the limb 

 into a wing is confined to and concentrated upon the fifth digit, ib. 

 5 : its metacarpal presents almost the thickness of an antibrachial 

 bone : the proximal phalanx, of equal thickness, has more than 

 twice the length, and at the proximal joint shows a process like 

 an olecranon. This is usually followed, as in Pterodactylus 

 crassirostris, by three similarly elongated phalanges, of which the 

 last gradually tapers to a point. The fore limb thus exceeds in 

 length the whole body, and is presumed to have supported a 

 membranous wing, as in the sketch a, fig. 111. 



Such are the chief modifications by which the fore-limb, in the 

 Reptilian series of cold-blooded air-breathers is or has been 

 adapted for aquatic, amphibious, terrestrial, arboreal, and aerial 

 life. Before, however, quitting this subject, it may facilitate the 

 comprehension of the homologies of the carpal series of ossicles, 

 by concluding with a separate and serial review of them in the 

 Reptilian group. 



In the Toad (Bufo) the carpus includes eight bones : the two 

 principal are the ' lunare,' fig. 44, C, Z, and ' cuneiforme,' ib. c, 

 respectively articulating with the radial and ulnar divisions of the 

 antibrachial bone, ib. 54, 55 ; the scaphoid, c, s, presents its * inter- 

 medial' position between the lunare and the four ossicles on the 

 radial side of the distal series : these consist of the trapezium t, 

 trapezoides tr, magnum m, and the divisions of the unciform ?^ for 

 the fourth and fifth digits ; that for the fifth being the largest 

 of the five bones. The thumb, I, is represented by its metacarpal 

 only ; the index, fig. 44, A, n, and medius, ill, have each a 

 metacarpal with two phalanges ; the digits iv and v have each 

 three phalanges. 



In the Tortoise (Testudo, fig. 108), the antibrachium articulates 

 with three carpals forming the proximal row ; the first or radial 

 bone, ib. a, answers to the ' scaphoid ' with the ' intermedium ' e ; 

 the second ib. c, to the lunare ; the third, ib. d, to the cunei- 

 forme ; the lunare being interposed between the ends of the radius 

 and ulna. In the Emys, fig. 51, s, the carpus has a similar struc- 

 ture ; but in some species there is a distinct pisiforme. In the 

 Turtle ( Chelone), the scaphoid is reduced in size, and represents 

 only the intermedium, fig. 107, e; it is separated by the lunare 

 c, from the radius a, and is pushed into a position analogous to 

 that which its homotype the ' naviculare ' holds in the mammalian 

 tarsus. Without the light from the testudinate modification, 



vol. i. n 



