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Show 618 ON A SKULL OF DISTIRA CYANOCINCTA. [Nov. 18, Snake, Distira cyanocincta, from Ceylon, belonging to the Museum of the College of Surgeons, showing grooves not only upon all the maxillary teeth, as normal in that genus of Sea-Snakes, but also upon the mandibular teeth. The groove on the latter teeth, although very shallow, was yet perfectly distinct when viewed under an ordinary lens; it ran along the antero-outer side of the tooth. This appeared to be the first notice of grooved mandibular teeth in a Snake ; but the presence of a groove on the posterior maxillary teeth had been several times recorded in Sea-Snakes, for the first time by Thomas Smith, Phil. Trans, cviii. 1818, p. 472, who had remarked:-"In this Serpent (Hydrus), as in many others nearly allied to it (les Hydres of M . Cuvier), there are simple teeth on the same bone which supports the poisonous fangs. These teeth so much resemble the fangs, that it requires a very close investigation to distinguish between them ; and this arises from the simple tooth having not only a longitudinal furrow exactly resembling the edges of the slit of the poisonous fang, but also a very visible cavity at the base, where the foramen occurs in the others ; and I have even found a fine tube in a tooth of this sort; it was, however, confined to the parietes, and did not affect the cavity of the tooth." Mr. Boulenger also exhibited three skulls of the Green Turtle (Chelone ?nydas), likewise from the Museum of the College of Surgeons. In one of these the prae- and postfrontal bones were in contact, excluding the frontal from the periphery of the orbit; in another, the frontal separated the prefrontal from the postfrontal; whilst in the third, the former disposition was shown on the right side and the latter on the left. Attention was drawn to the variability of this character, because it had recently been proposed to make use of it for diagnosing the genera of Turtles, the genus Chelone, to which the Green Turtle belongs, being described by Baur (Am. Nat. 1890, p. 486) as having the " Orbit formed by prefrontal, frontal, postfronto-orbital, jugal, maxillary." It was further observed that the same variability occurs, though not so frequently, in the genus Thalassochelys. The skull of a half-grown Loggerhead from Ceylon, preserved in the British Museum, had the frontal bone excluded from the orbital periphery on the right side and not on the left. That specimen had, besides, the maxillaries separated by the vomer, instead of the maxillary suture commonly found in Thalassochelys ; a skull of Loggerhead in the College of Surgeons was, in this respect, intermediate between the two extremes, the praemaxillo-maxillary and maxillo-vomerine sutures forming an X-shaped intersection. Mr. G. A. Boulenger, F.Z.S., read a paper upon the Reptiles and Batrachians of Barbary (Morocco, Algeria, Tunisia), based chiefly upon the notes and collections made in 1880-84 by M. Fernand Lataste. This paper will be printed entire in the Society's ' Transactions.' |