e 
DESCRIPTION OF REPTILES. 221 
The finely-wrinkled character of the superficies of the bones in the cranium 
here described, smooth in comparison with that in Ch. breviceps, so closely agrees 
with that of the bones of the carapace and plastron of the Chelone convewa, de- 
scribed in my ‘ Report on British Fossil Reptiles*,’ that I shall provisionally 
refer the cranium to that species. 
Portions of a fossil carapace of a Chelone from Bracklesham, some of which 
are figured in Tab. XII. figs. 16 & 17, indicate a large individual of probably one 
of the two extinct species of the genus above-defined from the characters of 
their skull. Figure 18 shows two views of the mutilated head of a humerus : 
figure 19 gives two views of an ulna. Fig. 17 is an expanded neural spine of a 
dorsal vertebra, forming one of the median pieces of the carapace ; and fig. 16 is 
a portion of an expanded rib, forming one of the lateral pieces of the carapace ; 
all of a true Chelone. 
Genus Trionyx. 
The fragments of the carapace and plastron of a large Trionyx from Brackle- 
sham are also of a kind too imperfect to give at present more certain informa- 
tion than the genus of Chelonian reptiles to which they have belonged. Fig. 15, 
Tab. XII. shows part of the eighth expanded rib from the right side of the cara- 
pace. 
Figs. 12, 14 & 16, Tab. XIII., are views of a sacral vertebra of a Trionyz, from 
Bracklesham ; figs. 13, 15 & 17 are corresponding views of the homologous ver- 
tebra of a recent Trionyx of the same size. 
Amongst the remains of the genus Trionyx discovered at Bracklesham, ought 
to be specified a considerable portion of the right hyposternal, showing the cha- 
racteristic notch for the xiphisternal bone, the smooth inner surface and the 
rugous, worm-eaten character of the external surface. The thickness of this 
bony plate is from 3 to 5 lines, and indicates a species as large as the full-grown 
specimens of Trionya egyptiacus. A portion of the hyosternal bone of the same 
plastron was found with it. Remains of the Trionyx are more or less common 
at Hordle, Sheppey and the Isle of Wight; but they have not yet been noticed, 
so far as I am aware, in the eocene deposits at Bognor. 
* Report on Brit. Foss. Reptiles, p. 178. 
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