740 REPTILIA. 



across between the third and fourth costals. A vertebral ridge in the young rising 

 into two prominent nodosities on the posterior margin of the second and third 

 vertebrals. In adults, the ridge all but disappears, but the nodosities are visible ; or 

 the ridge is most marked on the first and last vertebrals and caudal. Caudal notch well 

 defined in the adult females, but apparently less so in the males. Nuchal small and 

 triangular, pointed in front and broad behind. The first vertebral is more elongated 

 than in the young, and in some it has a distinct hour-glass form, but in others the 

 anterior half of the hour-glass is much more contracted than the posterior half. 

 In this form it strongly resembles the first vertebral of B. thurgi. Its shape varies 

 considerably, as it is sometimes only as broad as long, while in others it is much 

 longer than broad. The suture between the first and second vertebrals is always 

 transverse. One of the most characteristic features of the vertebrals is the pointed 

 posterior extremity of the second plate, which projects inwards into the third plate 

 with a central nodosity. This plate is broader anteriorly than posteriorly, and its 

 breadth may equal its length, or it may be broader than long. The character of 

 this plate in the adult (in some young examples the backwardly pointed form of 

 the second vertebral is not so well defined), enables the species at once to be dis- 

 tinguished from the other two species of black-lined Batagurs, B. trivittata and 

 B. thurgi, in both of which the sutures between the first and second, and second 

 and third vertebrals are transverse. There are many other features by which they 

 can be separated, but these shield characters sufiice to distinguish B. duvaucelli. 

 The third vertebral is deeply emarginate on its anterior border, and its greatest 

 length equals its breadth. The fourth vertebral is long, with a transverse suture 

 between it and the plate before and behind it, and it is generally a little narrower 

 anteriorly than posteriorly, and in this is like B. lineata. In the character of its 

 second vertebral, it is closely approached by the so-called genus Bangshura. The 

 greatest breadth of this plate falls short of its length, and its general character is 

 to be dilated at its middle, and sHghtly contracted at its ends. In B. thurgi, this 

 plate is short and broad, while in B. trivittata it is long as in B. duvaucelli, and in B. 

 iravadica it is also somewhat long, as in B. lineata, its Western representative. 

 The fifth vertebral is broader than long, with a somewhat rounded anterior margin, 

 equalling about one-half the length of the plate, and with a nearly straight, 

 sinuous, or posteriorly concave fourth costal border. It is in contact with a small 

 portion of the tenth marginal. 



In the young, the posterior margin of the shell is strongly serrated from 

 the eighth to the twelfth marginal, but this serration entirely disappears in the 

 adult. 



The carapace of the male is considerably more depressed, and not so deep as the 

 carapace of the female. 



The sternum of the male is narrower and more elongated anteriorly than in 

 females of the same size, and has a less axiUary and inguinal breadth. The sternal 

 ridge is weU developed in the young, but disappears with age, and is obsolete in 

 females measuring 7"-ll, with a faint trace of it in males a little larger than this. 



