436 CHELONIA. 



Thalassoclielys olivacea, FiTZ. in Zool. Ann. Wien, Mus. I, 1841, 128. 

 Lepidocheli/8 olivacea, FiTZ, Syst. E,ept. i, 1843, 30. 



Caouana olivacea, Gray, Catal. Tort. Croc. & Amphisb. Brit. Mus. 1844, 53 ; &, 

 Catal. Shield. EepK Brit. Mus. 1855, 78. . ' 



Obsery. — Eschscholtz, who was the first to describe this species, 

 speaks of two specimens which fell under his observation : a young 

 and an adult. According to his own statement, these specimens ex- 

 hibited various differences, which might have been looked upon as 

 specific, had he not made a comparative study of them. Thus, the 

 width of the carapax when compared to its length, is smaller in the 

 adult than in the young. The young exhibits a prominent ridge 

 along the vertebral line, produced behind in the shape of a spine, and 

 which is no longer observed in the adult, except that the first and 

 fifth vertebral shield are rather convex. The costal shields are seven 

 on either side in the adult, and in the young six on the left side, and 

 seven in the adult. The lateral edges in the adult are horizontal. 



The cephalic plates are identical in both the young and the adult, 

 the latter, however, exhibiting an additional odd occipital plate, thrust 

 between the hind part of the postoccipitals. The margin of the jaws 

 is even in either case. The adult is provided with a blunt nail to 

 each fore and hind flipper, whilst the young is clawless. 



Most of these difierences, however, are of minor importance, with 

 the exception of one, which teaches a morphological fact of great 

 value : we refer to the presence of a blunt nail or claw in the adult, 

 and which the young does not possess. Hence we may conclude, that 

 when the young exhibits any claws whatever, the latter are likely to 

 be found in the adult. 



The first pair of cephalic plates might be taken for a third pair of 

 frontals, from the fact of their being contiguous upon the middle line 

 of the cephalic region, and situated in advance of the vertex plate. 

 Whichever be their appellation, the distinctive mark remains the 

 same. Three pairs of contiguous plates are observed in advance of the 

 vertex plate, which is elongated and hexagonal. 



The digits are mostly naked or scaleless ; the rest of the paddle, or 

 anterior portion of the limbs, is protected by conspicuous scales. 



Log. — Chinese Seas. 



