3.54 



ZOOLOGY 



SECT. 



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

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

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



which the most ventral and pos- 



-P7i* 



FIG. 995. Tarsus of Emys europaca 

 (right side) from above. J-\ fibula ; T. 

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

 proximal row ; Ph'. first phalanx of the 

 fifth digit; 14. distal tarsals; IV, 

 metatarsals. (From Wiedersheim's Com- 

 2iamtive Anatomy.) 



terior ray, ending in a free ex- 

 tremity, is the coracoid ; while 

 the other two are the scapula and 

 a process, sometimes regarded as 

 representing the procoracoid, 

 given off on the inner side of the 

 scapula near its glenoid end. The 

 bones of the carpus have nearly 

 the typical arrangement, consist- 

 ing, as in Lizards, of a proximal 

 row of three, a distal row of five, 

 and a centrale between the two. 

 The pelvis resembles that of 

 Lacertilia, except that it is broader 

 and shorter. Both pubes and 

 ischia meet in ventral symphyses, 



and epipubic arid hypo-ischial cartilages may be present. In the 



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



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

 In the Grooodiiia also the clavicle is absent, but there is an 



episternum. The number of carpal ele- 

 ments is reduced, the largest being two 



proximal bones, the radiale and the ulnare 



(Fig. 996, r, u.J). 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 



Reptiles, and the parts have been variously 



interpreted. Two bones (P), which are 



usually regarded as the pubes, extend from 



the region 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 (Jfir). The posterior ends 



of the pubes are cut off from the acetabulurn 



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 backwards 



from the acetabula and are fixed together ventraliy (at Sy.) but 



Fin. 99(5. Carpus of young 

 Alligator. C. centrale 



(?) ; R. radius ; U. ulna ; r. 

 radiale ; u. ulnare ; 1 5, 

 the five distal carpals(not. 

 yet ossified) ; 1 and ~1 

 united into one, and also 

 3, 4 and 5 ; t, pisiform ; 

 7 P, the five metacarpals. 

 (From Wiederfheim's Com- 

 jini'ntlf'e Anatomy.) 



