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Show 1871.] MR. SCLATER O N T H E SHELL OF A RIVER-TORTOISE. 325 Port-Jackson Heads and the mouth of the Clarence River; and it probably ranges further north. DESCRIPTION OF PLATE XXXIV. Figs. 1, la. Helix alfredi, p. 323. I Fig. 4. Voluta kingi, p. 324. 2, 2 a. millicentcB, p. 323. 5. coniformis, p. 324. 3. Bulimus hargravesi, p. 323. j 6. punctata, p. 324. May 2, 1871. Tbe Viscount Walden, President, in the Chair. Mr. Sclater exhibited the shell of a River-tortoise of the genus Pelomedusa from the Upper Zambesi, and made the following remarks upon it: - " Mr. E. L. Layard has placed in my hands for examination the shell of a River-tortoise obtained on the Upper Zambesi by Mr. J. Chapman during his well-known expedition, which seems to indicate the existence in that district of a species of Pelomedusa more nearly allied to P. gehafie oi Eastern Africa than to P. galeata, the common species of the Cape Colony. In P. galeata the two pectoral shields of the thorax unite in the middle line and form a suture which is nearly two-thirds of the length of the suture between the two abdominal shields. In P. gehafie the pectoral shields terminate on their inner sides in angular points, which do not meet together in the middle line, so that the brachial shields join on to the abdominal and entirely divide the pectorals from the middle line. This is shown well in Riippell's figure (Neue Wirbelth. Amph. t. 1), in a living specimen of P. gehafie in the Society's collection, and in all the examples of this species that I have yet seen. In the present specimen, however, the pectorals come very nearly, if not quite, up to the median line; and there is also some difference in the shape of the other plates, the gulars and intergular being broader and not so deep. Under these circumstances I was inclined to think that the Zambesian Pelomedusa might be referable to a distinct species, especially looking to the very different locality. But Dr. Peters, who has been kind enough to compare the specimen with those of P. gehafie in the Berlin Museum, finds amongst the latter one from Sennaar which approximates to the Zambesian example in the pectorals running nearer together, so that I am not willing to found a new species upon a single shell. " It would be advisable, however, that more examples of the Pelomedusa of the Upper Zambesi should be obtained, and further comparisons made, as the extension of a species hitherto considered |
