1871.] MR. SCLATER ON THE 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<z. millicentm, p. 323. , 5. cotriformis, p. 324. 



3. Bui imus kargravesi, p. 323. | G. punctata, p. 324. 



May 2, 18/1. 

 The 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 re- 

 marks 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 nearlv 

 allied to P. gehafie of Eastern Africa than to P. galeata, the com- 

 mon 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 abdo- 

 minal and entirely divide the pectorals from the middle line. This 

 is shown well in Ruppell's figure (Neue Wirbelth. Amph. t. 1), iu 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, espe- 

 cially 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 pec- 

 torals 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 Pelo- 

 medusa of the Upper Zambesi should be obtained, and further com- 

 parisons made, as the extension of a species hitherto considered 



