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Show 68 DR. J. E. GRAY ON THE TRIONYCHlDcE. [Jan. 7, A specimen in spirits, figured in the Cat. Sh. Rept. t. 30, received from Utrecht, with the dorsal disk about six inches long, does not show any indications of callosities, though it is quite as large as the two dried specimens in the British Museum (one from the same collection), which have these callosities well developed. This genus seems peculiar in having the front margin of the thorax rounded and its sides dilated so as partly to hide the feet when they are withdrawn. A specimen from the Lao Mountains, collected by M . Mouhot (59, 7, 8, 8), mentioned under Aspilus ornatus (Suppl. Cat. Sh. Rept. p. J 03), evidently belongs to this species. Three young specimens from Ceram and Amboina have the callosities not developed. The white spots on the head and the large ones on the throat are so like those of larger specimens from Java in spirits in the British Museum, that I think they will prove to be only a younger state. There is a young specimen in the British Museum, obtained from Mr. Bartlett, in spirits, the dorsal disk of which is pale brown, with large scattered pale spots, with ridges of lines, which are separated from one another, and larger in the hinder part of the disk. There is a bleached specimen in spirits received from the Leyden Museum, which is very like a specimen figured in the ' Fauna Japonica.' Dorsal disk about six inches long and wide. It has no indications of the sternal callosities; and the form of the bones is seen through the skin. I think it most likely belongs to this species. There is a rather smaller bleached specimen in the Museum, in spirits, received from Amboina. II. Emydina. The hinder lateral edge of the sternum with flaps to cover the hinder feet ; front pair of bones of the sternum with callosities; the front odd bone of the dorsal disk united to the ribs, and sometimes with a small free bone in the margin before it. The similarity of the jaws and of the shape of the living Cyclan-osteus which I had lately an opportunity of examining and figuring from life (P. Z. S. 1870, t. 43), to the animal of Emyda, is so great that I think they should be ranged in one group, and the family which I called Emydidee, because the dorsal disk was armed with bones, should be abolished. Some of the genera also have a rudimentary marginal bone in the front of the disk, as in Emyda, which has also posterior marginal bones. These animals have the odd bone in front of the back united to the ribs in the adult age, so as to form a complete dorsal disk. The genera Cyclanosteus, Emyda, and Heptathyra of the former family have, in addition, a single bone in the centre of the front margin, which is distinct from the front of the odd bone ; but the latter often has a notch in the front margin to receive part of it. This bone, I suppose, is a remnant of the marginal bones present in the other |
