TAB. XII. 

 Chelone crassicostata. 



View of the inner surface of the carapace, half the natural size. 



ch. The nuchal plate. 



ph. The first costal plate and adherent rib. 

 ph. The second ditto. 

 ph. The third ditto. 

 ph. The fourth ditto. 

 ph. The fifth ditto. 

 ph. The sixth ditto. 

 plj. The seventh ditto. 



ph. The eighth ditto. The figures are placed above the free projecting ends of 

 the ribs ; they belong to the second and the ninth dorsal vertebrae 

 inclusive. 

 s9- The ninth neural plate. 

 ■s'10. The tenth neural plate. 

 py. The last neural or the " pygal" plate. 



These are developed, like the nuchal plate, in the substance of the derm, 

 and do not become confluent with any parts of the endoskeleton. 



