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Show 1873.] DR. J. E. GRAY ON THE TRIONYCHlDcE. 65 sities, like the Trionyx, very unlike the narrow transverse callous band on the edges of the central suture in Aspilus. The hinder sternal bones are smooth. The skull is exceedingly like that of Trionyx; but the front of the upper jaw is broader and rounded in front. The distance between the orbit and large quadrangular transverse nose-hole is notlialf the length of the diameter of the large orbit. The alveolar surface of the upper jaw is moderate, rather narrow in front, and gradually rather broader at the hinder part. The longitudinal depression in front of the inner nostrils is moderately deep, rounded in front, and rather broader behind. 1. RAFETUS EUPHRATICUS. (Fig. 12, p. 66.) Testudo rafeht, Oliv. Voy. Pers. ii. p. 453, t. 41 (copied, Shaw's Miscell. t. 2. p. 907). Testudo euphraticus, Daud. Rept. ii. p. 305 (from Olivier). Trionyx euphraticus, Geoff. Ann. Mus. iv. p. 17 (from Olivier). Gymnopus euphraticus, Dum. et Bibr. Erp. Gen. ii. p. 498. Tyrse rafeht, Gray, Cat. Tort. Brit. Mus. p. 49. Trionyx rafeht, Gray, Cat. Sh. Rept. Brit. Mus. p. 85, t. 30. Rafetus euphraticus, Gray, P. Z. S. 1864, p. 81, 1869, p. 213; Suppl. Cat. Sh. Rept. p. 104. Hab. Euphrates (Chesney and Loftus); Tigris (Olivier). C. Dorsal disk truncated in front, with the odd bone separate from it, and with a rounded central callosity in the adult; lateral bones of the sternum expanded, with a narrow linear callosity on each side of the central suture; posterior pair of bones slender, not dilated, without callosities. The dorsal disk is truncated or concave on the front edge; the front edge of the first vertebral bone is generally rounded and prominent in front towards the rounded callosity in the middle of the separate front odd bone. ASPILUS. Aspilus, Gray, P. Z. S. 1864, p. 84, f. 4-6 ; Suppl. Cat. Sh. Rept. p. 102, f. 33 (skull). Skull tapering in front; the short space between the square nose-hole and the orbits less than half the diameter of the latter, which are large and rather close; palate broad, rather deep, of the same width the whole length ; alveolar process broad behind, gradually narrower in front. Lower jaw with a concave alveolar surface, rather broad in front, with a ceutral longitudinal ridge, more prominent in the centre of its length, and with a somewhat deeper concavity on each side of the ridge. The young specimens have the odd bone in front of the dorsal disk separate, smooth, and covered with the skin. In the older specimens it becomes nearer to the front edge of the dorsal disk, and has a small circular central callosity. PROC. ZOOL. Soc-1873, No. V. 5 |