294 
TERTIAIIT YERTEBRATA OF THE FAYCM. 
oval in ontlinc and slightly wider ])ostcriorly than anteriorly ; its convexity is not very 
great, though tlie crusliing, 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 
res])onsible for the flattened form of the shell. 4'here are six neurals (N.), of which the 
anterior five are hexagonal, with the antero-lateral borders much the shortest; the 
sixth (-A'". b) is pentagonal, its posterior angle being thrust between the anterior part of 
the sixtli 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 
])reserved. The suprapygal (P^. 1) is triangular, with the postero-lateral angles 
truncated for union with the last pair of marginals ; the pygal (l*y. 2) is nearly as 
wide as long. Tlie vertebral shields (i;.) 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 ento[)lastron is rather longer, the postero-lateral borders being 
longer than the antero-lateral ones. The sutures between the epiplastrals [Ep.p.) and 
hyoplastrals [Hyp.) are strongly concave forwards. The posterior ends of the humeral 
shields {]>.) do not reach so far back as the middle of the entoplastral, and the 
grooves between tliem and the pectoral shield [pect.) do not curve backwards, and 
so do not cross the suture between the epiplastrals and hyoplastrals. The small 
mesoplastra {Msp.) are rouglily 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 
xi])hiplastra with one another are almost equal in length. The dimensions of this 
shell are given below. 
C. 10202. Anterior portion of plastron. Type specimen figured and described in Ann. & 
Nat. Hist. [7] vol. xi. (l‘.)03) ]>. 121, pi. viii. tig. 2 c, the figure being reju'oduced as 
text-iig. 93. The dimensions (in centimetres) of this specimen are approximately ; — 
Width of anterior lobe immediately in front of bridge . . . ll'o 
Length of anterior lobe T’.l 
„ entoplastron 3'7 
C. 8509. Anterior portion of })lastron. In this the humero-pectoral groove does not cross the 
suture between the ejn- and hyoplastral hones, hut terminates with it on the lateral 
border. The ento])lastral 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 T'o cm., the 
length of the entojilastron 4'7 cm. 
R. 3103. Anterior j)art of ])lastron similar to the type sjiecimcn, except that the suture between the 
e])i- and hyo])lasti’al hones is more concave forwards and just touches the humero- 
jx'ctoral groove on the border of the plastron ; the entoplastral is larger and its postero- 
lateral hoi’d('rs are convex. 
