3o8 



nine plastral bones. Nuchal plate without rib-like processes. 

 Limbs paddle-shaped, with one or two claws. 



Marine. The eggs are soft-shelled, round (fig. I02a), and are 

 laid in the sand. 



Key to the I n d o-Aust ralian genera. 



A. Four pair of costal shields I. Chelonia p. 308. 



B. Five or more pair of costal shields 2. Caretta p. 310. 



I. Chelonia Brogn. 



(Brognart, Bull. Soc. Philom. Ill p. 89, 1800). 



Head with symmetrical shields. Carapace with fontanelles 

 between the costal and the marginal plates; nuchal shield 

 trapezoid; four pair of costal shields. Intergular and a series 

 of inframarginal shields present. Limbs paddle-shaped, with 

 one or two claws. 



Distribution. Tropical and subtropical seas. 



Key to the Indo-Australian species. 



A. Dorsal shields juxtaposed; one pair of praefrontals ; 



usually one claw; carapace unicarinate in the young, i. C. mydas p. 308. 



B. Dorsal shields imbricate; two pair of praefrontals; 



two claws ; carapace tricarinate in the young 2. C iinlwicata p. 309. 



I. Chelonia mydas (L.). 



Testudo mydas^ Linne, Syst. Nat. I 1766, p. 350. 



Chelone mydas, Boulenger, Cat. Chel. 1889, p. 180 (s. syn.). 



Chelonia mydas^ Siebenrock, Zool. Jahrb. Suppl. X 1909, p. 545 (s. syn.). 



Carapace tectiform or arched; with a median keel, and 

 sometimes a slight indication of a lateral keel in the young; 

 margin composed of 25 shields, not or indistinctly serrated; 

 dorsal shields juxtaposed; nuchal shield sometimes divided 

 into two; four pair of costals. Plastron rounded anteriorly; 

 intergular shield present; a series of large inframarginals. Snout 

 very short; jaws not hooked; horny sheath of upper jaw 

 striated interiorly and with a denticulated edge, of lower jaw 

 with strongly denticulated edge; alveolar surface of upper jaw 

 with two strong ridges, denticulated; mandibular symphysis 

 short; one pair of praefrontals. Tail short. Limbs flat, with one 

 claw; fore limbs long; young ones sometimes with a second claw. 



