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Show 220 DR. J. E. GRAY ON THE TORTOISES. [Mar. 1 1, These specimens are those referred to as having been sent from Chartoum by Mr. Petherick in the account of Tyrse nilotica in the P. Z. S. 1864, p. 88, where they were regarded as being specimens of the common Nilotic Mud-Tortoise ; but the examination of the alveolar surface of the jaws at once showed that they had no affinity with that genus, but must be more allied to the Gangetic Trionyx; and then I observed that they had the shorter face of that group, which character had been previously overlooked. The alveolar surface of both jaws is very wide, nearly flat (not concave in front as in Trionyx gangeticus). The species is, no doubt, peculiar to the Upper Nile, and had not been before observed. The examination of the alveolar surface of D u Chaillu's specimen, which had been named Aspidonectes aspilus by Mr. Cope, showed that it was (as I had previously determined it to be) identical with Tyrse nilotica of the Lower Nile. The head and neck of this large specimen, when the skin was wet, showed that it was speckled with white like the true Nilotic Mud-Tortoise Tyrse nilotica. The sternal callosities rather differ in form from those of T. nilotica; the hinder ones are larger, and more acute behind. The last of the ribs are also wider, compared with the others, than in that species. A young specimen in spirit, from the Upper Nile, obtained from Mr. Petherick, probably belongs to this species. The head, neck, feet, and dorsal disk covered with close, small, dark-edged, annular white spots, those on the sides of the head and, especially, on the chin and throat being rather the largest. 5. SARBIERIA. Head rather large; eyes lateral, subsuperior. Jaws strong; alveolar surface (of beak) broad, broader and more dilated behind, surface shelving inwards,-of lower jaw deeply concave, smooth, and with a sharp edge in front, and slightly concave on the sides. The central anterior palatine groove narrow and deep, with a short slight dilatation iu front and with rather diverging sides behind. Dorsal disk small. Costal bones separate. Front odd bone in the young and half-grown specimens separate, broad, transverse, and with a smooth upper surface. Sternal callosities four ; lateral narrow on the outer side ; anal ? This genus is in many respects allied to Dogania ; but it appears to have four callosities, and the upper surface of the back is concave ; it is narrow in front, and wider behind. But it is difficult to compare a head with the beak on with a prepared skull without a beak. SARBIERIA FRENATA. Trionyx frenatus, Gray, Cat. Shield Rept. p. 67. Potamochelys? frenatus, Gray, P. Z. S. 1864, p. 87. Hub. Singapore (Wallace). A stuffed specimen in the British Museum, " of a young female with full-sized eggs," from Mr. Wallace. The odd bone in front of the dorsal disk entirely covered with the skin, and smooth. The > |
