D. M. 8. Watson—Chelonian from, the Purbeck, Swanage. 313 
and hypo-plastra with the fourth to eighth marginals, and probably also 
by short and narrow buttresses; the evidence for these is that they 
have formed marked prominences on the carapace during the crushing 
which the specimen has undergone. The evidence suggests that the 
axillary buttress came down on to the first costal, and the inguinal 
buttress was fixed to the fifth and sixth costals at their junction, but 
chiefly to the sixth. 
The sulci marking the limits of the epidermal shields are ate 
obscure and only slightly impressed on the bones. So far as I have 
been able to determine them they are entered on Text-figs. 1 and 2. 
The nuchal shield is, however, quite distinct in both the Manchester 
specimens. The evidence appears to show that there were no supra- 
marginals and that the marginal shields lapped slightly on to the 
costals. On the plastron the sulci are easier to make out; there is 
a series of infra-marginal shields carried almost entirely on ‘the hyo-, 
meso-, and hypo-plastra. 
Fig. 2. Plastron of Glyptops ruetimeyeri (Lyd.). An unrestored -drawing of 
L. 9520. + nat. size. 
That the turtle I have described above is identical with Lydekker’s 
Thalassemys ruetimeyert there can be no reasonable doubt ; the contour 
of the carapace and the distribution of the epidermal shields, so far as 
they can be made out, the form and relations of the nuchal and first 
suprapygal are very similar, and with the exception of the occurrence 
of a preeneural in the Manchester specimens, such slight differences as 
there are can be easily accounted for by the fact that the type- 
specimen is rather smaller than the new specimens, and is therefore 
presumably rather younger. The plastron, containing as it does 
large and well-developed mesoplastra, at once removes the species from 
