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Show 1869.] DR. J. E. GRAY ON THE TORTOISES. 187 A second half-grown specimen agrees with the very large old specimen above noticed in the absence of the zygoma. 2. MELANOCHELYS. The thorax oblong, three-keeled. Vertebral plates broad, six-sided. Skull rather depressed; zygomatic arch imperfect, tapering behind, and not reaching the tympanic bone ; lower jaw weak ; the alveolar surface narrow, linear. Toes strong, webbed to the claws. MELANOCHELYS TRIJUGA. Emys trijuga, Gray, Cat. Shield Reptiles in B.M. t. 37. f. 2 ("E. subtrijuga," not good, zygomatic arch too broad and extending to the ear-bone). Skull (as seen through the skin in the stuffed specimen) ovate, elongate, triangular in front; sides of the face nearly erect; orbit lateral, subsuperior, large; nose rather narrow; crown rather convex, elongate rhombic, narrowed and produced behind; from the Melanochelys trijuga. hinder point to the back edge of the orbit more than once and one-half the distance of the latter from the end of the nose ; zygomatic arch rudimentary, very slender, linear, extending from the middle of the back edge of the orbit to the upper part of the front edge of the large tympanic cavity, which has a narrow, rounded edge; sheath of the upper jaw with a simple straight edge, without any |