64 
INDIAN TERTIARY AND POST-TERTIARY VERTEBRATA. 
Description.- — The specimen on which this species is founded is represented in 
plate XIII. The greater portion of the carapace remains, but a large part of the 
right side and the whole of the posterior extremity are wanting ; the vertebral and 
costal bones are distinctly defined, as are the boundaries of the anterior marginal and 
first three vertebral horny shields. Only small fragments of the plastron are pre- 
served, although sufficient remains to show that this was united by bone with the cara- 
pace, and that the band of union was a comparatively long one. When complete the 
total length of the carapace must have been about thirty-five inches. 
In the epidermal shields the most noticeable point is the absence of the nuchal ; 
the first vertebral is wider transversely than it is long ; while the second and third are 
imperfectly hexagonal, and are elongated antero-posteriorly. In the underlying 
bones the nuchal is of comparatively small size, and lies well within the limits of 
the first vertebral shield. There are seven vertebral bones, of which the first five 
are elongated, while the seventh is very small, and wedged in between the sixth and 
seventh costals. Behind the last vertebral the seventh and eighth costals unite in 
the median line; behind which there is the commencement of the supra-pygal 
bone, of which the hinder half is wanting. The contour of the carapace is sub-oval, 
the posterior portion being the narrowest; and the median line is much elevated, 
with the costals sloping rapidly away on either side : there is no keel on any of the 
vertebral bones. 
Affinities. — It is quite clear from the general structure of the specimen that the 
only families to which it could possibly belong are the typical Emydidce or the Chely- 
didce ; and it is extremely unfortunate that the decisive evidence which would be 
afforded by the plastron is not available. The characters of the carapace are, how- 
ever, such as to indicate clearly that it is to the latter family to which it should be 
referred. In the first place, the nuchal bone is of the relatively small size charac- 
teristic of the Chelydidce ; and in the second, the vertebral bones agree precisely in 
number and character with those of the Podocnemis group ; while there is the same 
interval between the last vertebral and the supra-pygal bones, and the latter was 
evidently a single one. If indeed the figure of the Indian specimen be compared 
with that of the so-called Platemys bowerbanki given by Owen 1 (which, as we have 
already mentioned, is referred to Podocnemis), it will be seen that the two evidently 
belong to the same group, and might perfectly well be generically identical, 
although their specific distinctness is indicated by the wider vertebral epidermal 
shields of the Engik'n form. If again the figure of the present specimen be compared 
with that of Podocnemis dumeriliana given by Gray , 2 an equally striking resem- 
blance will be observed in the general contour of the carapace, as well as in the 
absence of a nuchal shield ; and there accordingly appears no doubt but that the 
specimen belongs to the Chelydidce. With regard to its generic position, the presence 
of seven vertebral bones differentiates it from all the existing Australian genera; 
1 Op. cit., pi. XXIII. 
2 Cat. Shield-Reptiles in British Museum, pt. I, pi. XXVIII (1855). 
