336 



ZOOLOGY 



SECT. 



Reptiles, the first pair (epiplastra) to the clavicles, the others pro- 

 bably being of the same character as the abdominal ribs of the 



Crocodilia. 



The carapace of 

 the Luth or 

 Leather- backed 

 Turtle (Dermato- 

 chelys orSphargis) 

 is distinguished 

 from that of the 

 rest of the order 

 in being composed 

 of numerous poly- 

 gonal discs of bone 

 firmly united to- 

 gether, and in not 

 being connected 

 with the endo- 

 skeleton ; in the 

 plastron the 

 median bone is 

 absent. 



Carapace and 

 plastron are firmly 

 fixed together by 

 bony union in 



FIG. 997. Cistudo lutaria. Skeleton seen from below ; the \ , 



plastron has been removed and is represented on one side, m O S t instances, 



C. costal plate; Co. coracoid ; e. entoplastron (episternum) ; V>nf onTYiafimac! fV.o 

 Ep. epiplastron (clavicle ?) ; F. fibula ;Fe. femur ; H. humerus ; 



Hyp. hyoplastron ; Hpp. hypoplastron ; Jl. ilium ; Js. ischium ; connection is liffa- 



M. marginal plates ; Nu. nuchal plate ; Pb. pubis ; Pro. pro- 

 coracoid or process of scapula ; PH. pygal plates ; R. radius ; So. 



; T - 



mentous. 



The sternum in 

 the Lacertilia is a 



plate of cartilage with a simple or bifid posterior continuation 

 formed by the fusion of five or six pairs of ribs. In the Ophidia 

 and Chelonia it is absent. ~ 



In the Crocodilia it is a 

 broad plate bearing the 

 coracoids and two pairs of 

 ribs with a posterior con- 

 tinuation which bifurcates 

 behind. 



A series of ossifications 

 the abdominal ribs lie 

 the wall of the ab- 



n 



FiG. 993. Chelone midas. Transverse section of 

 skeleton. C. costal plate ; C'. 1 centrum ; M. mar- 

 ginal plate ; P. lateral element of plastron ; R. rib 

 V. expanded neural plate. (After Huxley.) 



domen in the Crocodilia 



(Fig. 994, Sta), and similar ossifications occur also in the Moni- 

 Sphenodon, As already noticed, the posterior 



tors and in 



