4 CHKLONIA. 



Order CHELONIA. 



Chelonii'iis, Bnmfjniart, Bull. Soe. Philom. ii. 1800. 

 Testudiuata, Op'pel, Ordn. Rept. 1811. 



Quadrate bone imtnovably united to cranial arches. Dorsal ril)s 

 singlc-licaded, the anterior attached between two vertebra) ; body 

 encased in a bony shell, A plastron formed of a small number of 

 elements in addition to the clavicles. No sternum, Ko teeth ; jaws 

 covered -with horny sheaths. Anal opening round or longitudinal. 

 Copulatory organ present, single. 



Suborder I. ATHEC^. 



Ycrtebra) and ribs free, separated from a bony exoskcleton. f>kull 

 without descending processes of the parietal bones. 



Fam. 1. Sphargidse. Limbs paddle-shaped, clawless; ])halanges 

 ■without condyles. Exoskeleton consisting of numerous 

 small bony plates arranged like mosaic. 



Suborder II. THECOPHORA. 



Dorsal vertebrrc and ribs immovably united and expanded into 

 bony plates forming a carajiace. Parietals prolonged downwards, 

 forming a suture with the pterj-goids, or separated from the latter 

 by the interposition of the cpipterygoid. 



Siiperfam. A. CRYPTODIRA. 



Neck bending by a sigmoid curve in a vertical plane ; cervical 

 vertebra without or with mere indications of transverse processes ; 

 centrum of the last cervical articulating with the centrum of the 

 first dorsal. Mandible with ai'ticulary concavities; outer border of 

 tympanic cavity deeply notched ; pterygoids narrow in the middle, 

 in contact on the median line. Pelvis not anchylosed to the cara- 

 pace and plastron. Digits with not more than three ]ihalnnges. 

 Epiplastra in contact witli hyoplastra ; ento])lastron, if present, oval, 

 rhomboidal, or T-shaped. A complete series of marginal bones, 

 connected with the ribs. 



I. Digits short or moderately elongate ; phalanges with condyles; 

 claws four or five. Neck completely retractile. S(]uanjosal 

 bone widely separated from the parietal. 



A. Nuchal plate (bone) with costiform lateral processes, extending 

 below the marginals. 



Fam. 2. ChelydridaB. Caudal vertebra? mostly opisthoccclous ; pubic 

 symphysis widely separated from ischial. 



Fam. 3. Derniatemydidae. Caudal vertebra'' proca'lous : ])lastral 

 bones nine ; pul)ic symphisis widely separated from ischial. 



