CHELONIA. 229 



These facts agree with the slow growth of the body of the Tortoises, 

 and the great age which they attain. 



The Chelonians belong mainly to warmer climates, and live prin- 

 cipally on vegetables ; many of them, however, also live on Mollusca, 

 Crustacea, and Fishes. 



Fossil remains are first found, but rarely, in the upper white Jura. 

 More numerous remains are found in the Tertiary period. 



Fam. Cheloniadae. Turtles. With flat dorsal and often cartilaginous ventral 

 shield, between which the head and extremities cannot be retracted. The 

 latter are fin-like feet, with immovably connected digits, which are usually 

 without nails, and are covered by a common skin. The anterior limbs are much 

 longer than the posterior. Chelonia esculenta Merr. j Cli. {Caretta) imbricata 



. 647.Thalassochelys caretta (r&gne animal). 



L., Atlantic and Indian Ocean ; Thalassochelys caretta L. = corticata ftond. 

 (fig. 647), Atlantic Ocean and Mediterranean ; Spliargis coriacea Gray Karc 

 in the Mediterranean, more common in the Atlantic Ocean and South Sea 



Fam. Trionycidae. Soft or Mud Tortoises. With flat, oval, incompletely 

 ossified dorsal shield, and long retractile neck. Jaws with cutting edges, sur- 

 rounded by fleshy lips. The head and feet are not retractile. The nasal 

 openings are on the long snout. Trionyxferox Merr. A fierce animal. Found 

 in the rivers of Georgia and Carolina. Good to eat. 



Fam. Chelydae. Head and feet not retractile. Latter end with free digits. 

 which are webbed and furnished with claws. Chelys finibriata Schweig., 

 Matamata, South America. 



Fam. Emydae. Freshwater Tortoises. Dorsal shield flat, plastron usually 

 small. Feet thick, with freely movable digits, which are connected by a we) . 

 Thev swim excellently, and move also with great facility on land. They prin 



