FREE APPENDAGES REPTILES 



285 



Ophidia, with few exceptions, have lost all traces of paired append- 

 ages, but a few have retained the pelvis (p. 265) and some bones of 

 the hind hmbs, (fig. 286, D), interpreted as femur and tibia. 



Chelonia have a short, usually curved humerus, the head of which 

 is sometimes hemispherical, sometimes a roller, while distally there 

 is usually an entepicondylar foramen, and the trochlea is divided 

 into three condyles, and many species have a brachial patella (p. 277). 

 The ulna, smaller than the radius, has an olecranon, and both of 

 these bones are immovable on each 

 other in some species. The carpus 

 is primitive in nwst genera, inter- 

 medium and centrale (sometimes 

 two centraha) being separate, but 

 the radial centrale, when there are 

 two, may fuse with the radiale. A 

 pisiforme of varying size occurs. 

 On the distal side of the carpal 

 hinge the five carpaha are usually 

 separate, each supporting its 

 metacarpal. The digits are short 

 in terrestrial and fresh-water gen- 

 era, elongate in marine. The 

 phalanges are usually 2, 3, 3, 3 or 

 4, 2 or 3, rarely 2.2, 2, 2, 2. 



The femur, often curved, but 

 straight in marine genera, has a 

 hemispherical head at nearly a 

 right angle with the shaft, and 

 near it is a large fibular trochanter. 

 There are two distinct condyles at 

 the lower end, and sometimes a 

 patella. The tarsus is primitive in some, all nine bones being present, 

 but usually there is a fusion of tibiale, intermedium and centrale 

 (sometimes two centraha) to a tri tibiale (astragalus), the intratarsal 

 hinge passing between this on the one side and fibulare and tarsaha 

 on the other. Fusion is common between tarsalia 4 and 5, while 

 the fifth sometimes unites with the fourth or fifth metatarsal. 



Crocodilia. — The stout and slightly curved humerus is expanded 

 at both ends and has a strong radial (deltoid) crest. The trochlea 



Fig. 308. — A, Fore limb of Chelone 

 imbricata, and B, hind limb of C. midas 

 (Reynolds, '97). c, centrale; F, fibula; 

 /, fibulare; Fe, femur; h, humerus; i, in- 

 termedium; w, metacarpals and meta- 

 tarsals; p, pisiforme; R, radius, largely 

 hidden by ulna; r, radiale; T, tibia; //, 

 tritibiale; U, ulna; u, ulnare; 1-5, carpalia 

 and tarsalia. 



