442 MANUAL OF ZOOLOGY sect. 



of wide, flaps of skin at the sides of the body, acting as 

 wings or rather as parachutes. In Hatteria and Crocodilia 

 (Fig. 264) each rib has connected with it posteriorly a flat- 

 tened curved cartilage, the uncinate. 



Fig. 265. — ClStudo lutaria. Skeleton seen from below; the plastron has been 

 removed and is represented on one side. C. costal plate; Co, coracoid; e, ento- 

 plastron; Ep y epiplastron; F, fibula; Fe, femur; H, humerus; //, ilium; Is, 

 ischium; M, marginal plates; Nh, nuchal plate; Pb, pubis; Pro, pro-cora- 

 coid; Py, pygal plates; I?, radius; Sc, scapula; T, tibia; U, ulna. (From 

 Zittel.) 



In the Chelonia (Fig. 265) the total number of vertebrae 

 is always smaller than in the members of the other orders. 

 The cervical and the caudal are the only regions in which 

 the vertebras are movable upon one another. The vertebras 



