62 
INDIAN TERTIARY AND POST-TERTIARY VERTEBRATA. 
Hemichelys warthi, nobis. 1 
Characters. — Carapace depressed, expanded posteriorly, with five vertebral 
bones, and its surface comparatively smooth ; surface of plastron pitted ; length of 
carapace about 28 inches. 
Description. — The type specimen is represented in plate XII, and comprises 
the greater portion of the carapace and plastron. The former is tolerably perfect 
posteriorly, but has lost the greater portion of the lateral marginals, and anteriorly 
the nuchal bone, the marginals, and portions of the first costals; the figure is 
restored from the recent Podocnemis pipiti (Gray). 2 The plastron has lost both 
extremities, and its junction with the carapace is also injured. 
When entire, the carapace must have measured about 28 inches in length. The 
Pleurodirian affinities of the specimen are conclusively shown by the general contour 
of the carapace, which agrees very closely with that of Podocnemis pipiti, by the 
presence of only five vertebral bones, and of a single supra-pygal, as well as by the 
elongated form of the pygal and adjacent marginal bones. The surface of the 
carapace is moderately smooth, and shows no trace of the marks of horny shields ; 
the surface of the plastron (pi. XII, figs. 2, 3) is marked with small pits, and was 
evidently covered merely by skin. The only one of the plastral sutures that can be 
detected is that between the hyo- and hypo-plastron ; externally this suture divides, 
apparently for the reception of a small incomplete mesoplastron. 3 Whether the 
extremity of the xiphiplastron was forked as in the restoration, or whether it was 
entire as in Carettochelys , 4 cannot of course be determined. 
Affinities. — The absence of horny shields 5 from this interesting form conclusively 
separates it from all members of the Chelydidce, and affiliates it with Carettochelys. 
The latter is, however, widely distinguished by the characters of the vertebral bones 6 
which form minute elongated hexagons, separated from one another by portions of 
the costals, which consequently meet in the middle line ; the present form is also 
distinguished by the pitted sculpture on the plastron, and (apparently) the more deeply 
cut axillary notch ; while it is highly probable that the nuchal bone was of the form 
represented in the restoration, and was not of the curiously expanded shape 
occurring in the New Guinea genus, 7 which resembles that of the Trionychidce. 
These differences leave no doubt as to the generic distinction of the present 
form from Carettochelys , but the common feature of the absence of horny shields 
apparently indicates such relationship as to justify at least its provisional reference 
to the same family. While, however, Carettochelys is an extremely aberrant form 
1 Loc. cit. 
2 See ‘Proc. Zool. Soc.,’ 1871, pp. 747-48. 
3 Compare Owen’s figure ( op. cit., pi. XXIII) of the so-called Platemys bowerbanki. 
* Ramsay, op. cit., pi. III. 
s In the preliminary notice, I thought it probable that these plates were present on the carapace. 
6 Ramsay, op. cit., pi. IV. 
7 Ibid. 
