344 



ZOOLOGY 



SECT. 



On the ulnar side of the latter is a small accessory bone (pisiform,^). 

 The pelvic arch (Fig. 1008) differs somewhat 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 (BR). 

 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 ossi- 



7/ \!k^ J fied. The ischia extend down- 



wards and somewhat back- 

 wards from the acetabula and 

 are fixed together ventrally 

 (at Sy.), but there is no true 

 symphysis, as their extremities 

 remain cartilaginous. A hypo- 

 ischium is not present. In 

 the tarsus (Fig. 1009) there 

 are two proximal bones an 



JSR 



FIG. 1008. Pelvis of young Alligator, ven- 

 tral aspect. B, fibrous band passing be- 

 tween the pubic and ischiatic symphyses ; 

 BR. last pair of abdominal ribs ; F. obtu- 

 rator foramen ; O. acetabulum ; //. ilium ; 

 Is. ischium ; M. fibrous membrane be- 

 tween the anterior ends of the two innomi- 

 nate bones and the last pair of abdominal 

 ribs ; P. pubis ; Sy. ischiatic symphysis ; 

 /, //, first and second sacral vertebrae. 

 (From Wiedersheim's Comparative Ana- 

 tomy.) 



FIG. 1009. Tarsus of Crocodile (righ . 

 side) from above. F. fibula ; T. tibia ; 

 t. i. c. the astragalus, formed of the united 

 tibiale, intermedium and centrale ; /. 

 fibulare (calcaneum) ; 1 3, united first, 

 second and third distal tarsals ; 4, fourth 

 tarsal ; I IV, first to fourth metatarsals ; 

 VI, fifth distal tarsal and fifth meta- 

 tarsal. (From Wiedersheim's Compara- 

 tive Anatomy.) 



astragalo-scaphoid and a calcaneum the latter having a prominent 

 calcaneal process, and two distal tarsal bones, together with a 

 thin plate of cartilage supporting the first and second meta- 

 tarsals. The missing fifth digit is represented by a rudimentary 

 metatarsal. 



