THE PLASTRON OF THE CHELONIA . 



175 



and the two ^iplasira correspond with the median and lateral 

 thoracic plates of the Labyrinthodont A/mphibia, and very 

 probably answer to the interclavicle and clavicles of other 

 Vertebrata. 



Fig. 64 — The plastron of the Green Turtle {Chflaw miiUzs): Ld^ intercIaTide ; cZ, da^- 

 cies; ^.p^ hyoplastzon ; ^.j)., hypophstron ; J^., xiphiplastzon. 



The sacrum consists of two vertebrae. The expanded 

 sacral ribs are not anchylosed with the centra and arches of 

 their vertebrae. 



The tail is flexible, and consists of procoeloua vertebras. 





fte. 65. — ^External view of a section of the anditoryrc^Q of the skuH in aTnrlle (<7AcZ(wm 

 mida«)'. f. o-. fenestra ovaliB:/. r., fbn^tra rotonda; esa, asc, psc^ external, anterioi^ 

 ind jmBterifH* semicircuUu: capaU. 



