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Show 4 MR. G. A. BOULENGER ON CHELONIAN REMAINS. [Jan. 6, 2. On some Chelonian Remains preserved in the Museum of the Royal College of Surgeons. By G. A. BOULENGER. [Received December 8, 1890.] In the course of a recent examination of the osteological material preserved in the Museum of the Royal College of Surgeons, I have come across a few interesting specimens of extinct and fossil Che-lonians, hitherto overlooked or wrongly interpreted, which Professor Stewart has most kindly placed at m y disposal for description. 1. On the Skull of an extinct Land-Tortoise, probably from Mauritius, indicating a new Species (Testudo microtympanum). A skull without mandible, from the Hunterian Collection (no. 1058), differs considerably from that of any of the gigantic Land- Tortoises hitherto described. As it comes nearest to Testudo tri-serrata, Gthr. \ an extinct form from Mauritius, we may assume, in the absence of any information as to its origin, that it probably came from that or some neighbouring island. T. triserrata is the only species of Testudo known to possess two median ridges on the alveolar surface of the maxillary, and this character is shown on the skull for which the name T. microtympanum is proposed, in allusion to the very small tympanic cavity, which is one of its principal distinctive features. Another important distinction is to be found in the great backward prolongation of the palatines and vomers, the latter bone forming a suture with the basisphenoid. The following is a description of this interesting skull:- millim. Total length to extremity of occipital crest .... 135 Length to extremity of occipital condyle 102 Greatest width 98 Diameter of orbit 33 Interorbital width 45 Greatest diameter of tympanum 21 Frontal region convex ; interorbital width greater than diameter of orbit; prsefronto-frontal suture oblique, extending beyond the middle of the upper border of the orbit; suture between the prse-frontals not quite half as long as that between the frontals; only the anterior half of the parietals forms a flat surface, and the sagittal suture is all but obliterated. Postorbital arch rather slender, narrower than the zygomatic, which is formed by the post-frontal, the jugal, and the quadratojugal; postfrontal in contact with quadratojugal. Tympanum small, its greatest (vertical) diameter only about two-thirds the diameter of the orbit. Maxillary with 1 A. Giinther, 'The Gigantic Land-Tortoises (Living and Extinct) in the Collection of the British Museum ' (1877), p. 44, pi. xxii. fig. A. |