3.54 



ZOOLOGY 



SE( 



<i>ffc 



[C. 995.— Tarsus of Emys europaea 

 (right side) from above. F. fibula ; T. 

 tibia ; (i.)/. t. c. the united tarsals of the 

 proximal row ; P/t'. first phalanx of the 

 fifth digit ; 1—4. distal tarsals ; /— V, 

 metatarsals. (From Wiedersheim's Com- 

 2}arative Anatomi/.) 



clavicles are absent, unless, as is probable, the former be represent 



by the median element of the plastron and the latter by the fii 



lateral pair. The entire pectoral arch is a tri-radiate structure 



which the most ventral and pc 

 terior ray, ending in a free e 

 tremity, is the coracoid ; whi 

 the other two are the scapula ai 

 a process, sometimes regarded 

 representing the procoracoi 

 given off on the inner side of tl 

 scapula near its glenoid end. T. 

 bones of the carpus have near 

 the typical arrangement, consis 

 ing, as in Lizards, of a proxim 

 row of three, a distal row of fi\ 

 and a centrale between the tv. 

 The pelvis resembles that 

 Lacertilia, except that it is broad 

 and shorter. Both pubes ai 

 .ischia meet in ventral symphys( 



and epipubic and hypo-ischial cartilages may be present. In tl 



tarsus (Fig. 995) there is usually a single proximal bone and four di 



talia. There are never more than two phalanges in any of the digi 

 In the Crocodilia also the clavicle is absent, but there is i 



episternum. The number of carpal ele- 

 ments is reduced, the largest being two 



proximal bones, the radiale and the ulnare 



(^Fig. 996, r, «..). On the ulnar side of the 



latter is a small accessory bone (pisiform f). 



The pelvic arch (Fig. 997) differs some- 

 what widely from that of other living 



Keptiles, and the parts have been variously 



interpreted. Two bones (P), which are 



usually regarded as the pubes, extend from 



the I'egion of the acetabula forwards and 



inwards, but, though they become closely 



approximated anteriorly, do not meet in a 



symphysis. Between and in front of their 



anterior extremities, which are tipped with 



cartilage, extends a membrane {M) with 



which are connected in front the last pair 



of abdominal ribs (£r). The posterior ends 



of the pubes are cut off from the acetabulum 



by the interposition of a pair of bones which 



may be parts of the ilia, but are separately 



ossified. The ischia extend downwards and somewhat backwai 



from the acetabula, and are fixed together ventrally (at Sy.) h 



Fio. 99b.— Carpus of yov 

 Alligator, a conti 

 (?) ; R. radius ; U. ulna 

 radiale ; w. ulnare ; 1- 

 the five distal carpals( 

 yet ossified) ; 1 auc 

 united into one, and s 

 3, 4 and 5 ; t, pisifor 

 /— Vj the five metacarp 

 (From Wiedersheim's C 

 paratiee Anatomy.) 



