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Show 1869.] DR. J. E. GRAY ON THE TORTOISES. 205 terior end to the back edge of the orbit than from that part to the end of the nose ; eyes lateral, eyebrows rather convex ; zygomatic arch short, narrow, from the middle of the hinder edge of the orbit to the upper part of the front margin of the tympanic cavity, which is only furnished with a narrow edge. Sheath of the upper jaw with straight, closely denticulated edges ; lower jaw strong, very convex, and covered with a horny sheath in front. Toes slender, with a few hexangular shields above, very broadly webbed; claws small. 2. PANGSHURA TENTORIUM. Skull (as seen through the skin of the preserved specimen) very like that of P. tecta, but the crown is rather more produced behind, or rather the orbits are more in front of the head ; the bony temple is broader behind the eyes ; and the zygomatic arch is broader, being as wide as the upper half of the front edge of the tympanic cavity. The horny sheath of the upper jaw is rather sinuous, distinctly but closely denticulated. Toes slender, very widely webbed to the claws ; claws small. 3. PANGSHURA DURA. Skull (as seen through the skin of the stuffed specimen) ovate triangular, sides erect; orbit very large, subsuperior; crown rhombic, produced and acute behind, twice as long from the hinder end to the back edge of the orbit as the length from that part to the end of the nose ; zygomatic arch short, convex, the front end forming part of the crown, and wider than the orbit, and the hinder part narrower and only attached to the upper part of the edge of the tympanic cavity. Sheath of the upper jaw broad, high, with a straight simple edge; lower jaw strong, covered with a convex horny sheath in front. Toes slender, broadly webbed to the claws. Tribe VI. PSEUDEMYDINA. 19. PSEUDEMYS. 1. PSEUDEMYS SERRATA. A mounted skeleton in the British Museum, from North America. Skull solid, crown flat, produced and narrow behind, very broad, square, high in front, shelving to the mouth below; the labial edge nearly straight, with a notch in front, and minutely denticulated on the margin. The zygomatic arch very broad, slightly convex externally ; the mastoid bone produced horizontally, flat above externally, and keeled above, with a moderate-sized internal cavity. Palate concave behind the internal nostrils. The alveolar surface of the upper jaw flat, wide, rather produced behind; inner or palatine edge simple, and armed in front with a large tooth on each side of the centre, which is produced into a longitudinal sharp-edged irregular ridge parallel to the outer margin and nearer to it than to the inner edge of the alveolar surface. The lower jaw strong, much depressed and wide in front, and quite flat on the lower surface |