294 TEETIAET TERTEBEATA OF THE FATtM, 



oval in outline and slightly wider posteriorly than anteriorly ; its convexity is not very 

 great, though the crushing, which has resulted in the breaking away of a part of the 

 anterior border and the dislocation of some of the bones, may be to some extent 

 responsible for the flattened form of the shell. There are six neurals {N-), of which the 

 anterior five are hexagonal, with the antero-lateral borders much the shortest ; the 

 sixth {.W. 6) is pentagonal, its posterior angle being thrust between the anterior part of 

 the sixth costals, which behind it meet one another in the middle line, as also do the 

 seventh and eighth costals. The nuchal bone seems to have been wide, but is badly 

 preserved. The suprapygal (Py. 1) is triangular, with the postero-lateral angles 

 truncated for union with the last pair of marginals ; the pygal (Py. 2) is nearly as 

 wide as long. The vertebral shields (v.) are hexagonal, with, the anterior and posterior 

 borders convex forwards. Both in its general form and in its structure the carapace 

 is very similar to that of P. madagascariensis. 



In outline the anterior part of the plastron (text-fig. 94, B) is like that of the type 

 specimen, but the entoplastron is rather longer, the postero-lateral borders being 

 longer than the antero-lateral ones. The sutures between the epiplastrals [Ep.p.) and 

 hyoplastrals (IT^.p.) are strongly concave forwards. The posterior ends of the humeral 

 shields (h.) do not reach so far back as the middle of the entoplastral, and the 

 grooves between them and the pectoral shield [feet.) do not curve backwards, and 

 so do not cross the suture between the epiplastrals and hyoplastrals. The small 

 mesoplastra {Ms.p.) are roughly hexagonal in form ; the xiphiplastrals [Xi.p.) are 

 incomplete posteriorly, but the hinder border of the plastron was clearly deeply 

 notched. The median sutures between the hyoplastra, the hypoplastra, and the 

 xiphiplastra with one another are almost equal in length. The dimensions of this 

 shell are given below. 



C. 10202. Anterior portion o£ plastron. Type specimen figured and described in Ann. & Mag. 

 Nat. Hist. [7] vol. xi. (1903) p. 121, pi. viii. fig. 2 c, the figure being reproduced as 

 text-fig. 93. The dimensions (in centimetres) of this specimen are approximately ; — 

 "Width of anterior lobe immediately in front of bridge . . . 11-5 



Length of anterior lobe 7"5 



„ entoplastron 3'7 



C. 8509. Anterior portion of plastron. In this the humero-pectoral groove does not cross the 

 suture between the epi- and hyoplastr^l bones, but terminates with it on the lateral 

 border. The entoplastral is long ; its postero-lateral sides are convex. The approximate 

 width in front of the bridge is 12'5 cm., the length of the anterior lobe 7*5 cm., the 

 length of the entoplastron 4'7 cm. 



K. 3103. Anterior part o£ plastron similar to the type specimen, except that the suture between the 

 epi- and hyoplastral bones is more concave forwards and just touches the humero- 

 pectoral groove on the border of the plastron ; the entoplastral is larger and its postero- 

 lateral borders are convex. 



