10 CHELON1A. 



Group B. 



A single long neural between the first pair ofcostals; eighth costals 

 meeting behind the eighth neural. . Symphysis of mandible with a 

 median oral ridge. 



Crtonwr pfyauret, Theobald \ 



Carapace coarsely sculptured ; eighth costals produced laterally 

 and posteriorly into a projecting point ; plastral callosities very 

 slightly developed. 



For synonymy see Boulenger's 'Catalogue of Chelonians, &c.,' p. 251. 



Hab. Burma and (?) Borneo. 



R. 610. An imperfect carapace belonging either to the present or a 

 closely allied species ; from beds which are probably of 

 prehistoric or Pleistocene age at Paken Plat, Borneo. 

 This specimen, which wants the second, third, and fourth 

 neurals, and the last five costals of the left side, agrees in 

 all essential characters with the carapace of T. phayrei ; 

 although the sculpture is coarser than in either of the 

 two recent examples in the collection of the Museum, and 

 there is also a distinct median ridge in the four last 

 neurals which is not seen in those specimens. In the 

 absence, however, of a large series of recent examples, it 

 is not safe to say that those features are of specific value. 

 There is no evidence of the existence of T. phayrei in 

 Borneo at the present day. 



Presented by the Bornean Exploration Committee. 



Group C. 



A single long neural between the first pair ofcostals; usualh/ 7 

 neurals ; the eighth and hinder half of the seventh, costals meeting in 

 the middle line (fig. 8); Symphysis of mandible, when faioiun, with- 

 out oral ridge. 



In those cases where the entire carapace is unknown the reference 

 to this group is provisional. 



Trionyx aquitanicus, Delfortrie 2 . 

 Known only by a detached nuchal, neurals, and costals. Of large 



1 Trans. Linn. Soc— Zool. vol. x. p. 18 (1868). 



2 Act. Soc. Linn. Bordeaux, vol. xxvii. p. 417 (1869), 



