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Show 1893.] DR. 0. J. PORSYTH MAJOR ON MIOCENE SQUIRRELS. 179 1. On some Miocene Squirrels, with Remarks on the Dentition and Classification of the Sciurinee. By Dr. C. J. FORSYTH MAJOR, C.M.Z.S. [Received February 14, 1893.] (Plates YELL-XL) I. Introduction, p. 179. II. O n the Dentition of the Sciurinee, p. 179. III. Remarks on the Classification of the Sciurida?, p. 180. IV. Description of the Fossil Species, p. 190. V. O n tbe primitive Type of the Sciurine Molar, and of the Eutherian Molar in general, p. 190. VI. Explanation of the Plates, p. 214. I. Introduction. Ill order to determine some remains of Squirrels, collected by myself in the Middle-Miocene deposits of L a Grive-Saint-Alban (Isere), it was necessary to compare them with their actual congeners. I have to thank both Dr. A. Giinther and Mr. Oldfield Thomas for the kindness shown to m e in permitting a close examination of the rich collection of Sciurine skulls in the Zoological Department of the British Museum ; and I a m besides under great obligations to Mr. Thomas, w h o is so thoroughly acquainted not only with every species, but indeed with every specimen of the collection under his charge, for having liberally favoured m e with his experience and advice, especially in regard to intricate questions of synonymy and specific determination. The investigation of living forms has led m e somewhat farther than I had anticipated; so that before treating of the few fossil remains, it will be necessary to pass in review the numerous, aud, in several instances, very unexpected forms of Sciurine dentition, as well as to present some remarks on their classification. The brachydont teeth of Sciurinee presenting a very primitive type of Rodent molars, I was naturally led to consider them in the light of the prevailing theory, the so-called tritubercularity, the rodent molars having been traced, as those of other orders, to a trituberculate type. This forms the subject of the last part of m y communication. II. On the Dentition of the Sciurina?. It is a well-known fact that in various families of the Rodentia tubercular molars-which as a rule are brachydont-and laminated molars-which as a rule are hypsodont or rootless-are met with side by side in closely allied genera and in existing species, whilst in some other Orders we have to look among fossils for the more or less brachydont precursors of the living hypsodont forms. It is equally well known, though not always called to mind, 12* |