CHELONIA. 707 



The females, in 86 living specimens, were all smaller tlian the males,^ not so 

 elongated, deeper, with round backs and sides, and with the caudal plate not 

 prolonged so far downwards as in the male. There is also, generally, a nodose-like 

 ridge on the first vertebral, and the anal notch is more crescentic in form than in 

 the male, in which its margins are straight. The tail of the female is much shorter 

 than that of the male. 



The young is more rounded than the female, the posterior margin of the shell 

 is serrated, and the first and second marginals have their posterior external angles 

 terminating as outwardly and backwardly projecting spines, similar to those on the 

 posterior margin of the shell. 



The nuchal ^ plate is occasionally absent, and is very variable in size and form. 

 In some it is triangular, almost ungulate, and as broad as long, while from this 

 extreme on the one hand, it dwindles down through examples of every intermediate 

 grade into a narrow linear shield, hardly perceptible in some instances. The first 

 vertebral is as long as broad. In some, its lateral margins are straight and diver- 

 gent, so that it is broader anteriorly than posteriorly, while in others they are 

 slightly externally convex and the shield is as broad in front as behind. The first 

 marginal borders are anteriorly convergent, and the posterior margin is straight 

 and broad. The second and third vertebrals are alike in form, and much broader 

 than long, the breadth exceeding the length by one-half. The costal margins are 

 nearly equal in length, and the anterior and posterior borders are transversely 

 straight, the anterior border of the second being considerably narrower than the corre- 

 sponding margins of the third and fourth shields. The latter plate is not so much 

 broader than long, as contrasted with the former shields, and its hinder margin is 

 only a little more than half the breadth of its anterior margin. The fifth is less than 

 one-half of its length, broader than long, and all its margins are straight, the fourth 

 costal equalling the caudal margin in its extent. 



In the young, a distinct ridge occurs along the marginals between the axilla and 

 groin, and, in adult females, it exists interruptedly, while all trace of it is lost in the 

 male. In the young, the gular plates project slightly beyond the postgulars as two 

 rather nodose prominences. These shields are generally unsymmetrical, one being 

 larger than the other, and their relative length to the postgulars is variable, as they 

 sometimes equal the length of these shields, and at others excecid them.^ The 

 pectorals exceed the postgulars, but their breadth is subject to variation, and the 

 plates are occasionally unsymmetrical, one being considerably broader than the 

 other. The pectoral is the largest shield, and nearly equals the postgular and 

 gular. The preanal equals the gular and one-half of the postgular suture. Tlie 

 anal suture is very short, about one-fourth of the length of the gulars, and it is so 

 reduced in adult males as almost to be absent. The anal notch in the young is 



^ Hutton (Journ. As. Soc, Bengal, vol. vi, p. 689, 1837), in his observation on T. actinodes, states that the female 

 of that species considerably exceeds the male in size. 



^ In 86 living individuals of both sexes, the nuchal was absent only in four cases. 

 2 In an adult male they exceed the postgular by more than one-half of its length. 



