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Show 186 DR. C. J. FORSYTH MAJOR ON MIOCENE SQUIRRELS. [Feb. 28, of Elettaria (E. mollis, speciosa, and coccinea), as well as of some kinds of beetles and all sorts of caterpillars. A very similar food will in all likelihood hereafter prove to be preferred by Sc. Jwsei1. The molars of the semi-hypsodont Pteromys (Plates VIII. and IX. fig. 1.9) bear the same relation to those of Sciuropterus as the molars of the Xerus-type do to those of the Sciurus-vulgaris-type. In both, the valleys appear deepened and narrowed, but in Pteromys the narrowing is effected by the vertical increase of the wrinkles referred to in Sciuropterus molars (Plates VIII. and IX. figs. 20, 21, Plate IX. figs. 2, 5),-the result of which is that the cup of an inferior molar is filled up by these ramifications of the enamel, and the crown of both upper and lower molars becomes almost plane. The Eocene Ailuravus from Egerkingen (Switzerland)2, which I consider to be a Rodent, is in this respect somewhat intermediate between Pteromys and Sciuropterus. I have called the Xerus-type of molar a somewhat specialized one, and a m justified in doing so, as the teeth presenting it are no more brachydont-brachydontism being the primitive condition. The brachydont crown of Sciuromorpha is at the same time bunodont; whereas the semi-h) psodont teeth are more or less, and the hypsodont teeth are completely, lophodont. Another small group of Ethiopian Squirrels-Sc. stangeri (Plates VIII. and IX. fig. 7), Sc. ebii, and Sc, aubinnii (Plates VIII. and IX. fig. 8)-deserves the name of brachydont Xeri, as it shows from what form of brachydont molar the Zmt*-type may have originated. Other characters of this same small group to be mentioned presently likewise point towards the Hystricomorpha, notwithstanding their perfect brachydontism. In concluding these general remarks on the form of the Sciurine molar, I repeat what has already been stated, viz., that in perfectly brachydont Sciurine teeth the cusps tend towards a longitudinal arrangement-two marginal series in the lower molars; two marginal and one or more, more or less complete, intermediate series in the upper molars. This circumstance is of importance, as pointing towards the primitive arrangement of the molar cusps, and we shall have to revert to it when treating of the original type of molar. 111. Remarks on the Classification of the SCIURID.E. We have now to consider some of the bearings of the foregoing remarks on Sciurine molars on Classification. Classification was not m y original purpose ; but some of the results arrived at seem to m e of some interest in this respect too, so that I think they may be worth mentioning. Nor do I see why 1 Mr. Hose informs me that Sc. hosei is a ground-squirrel like Sc. insignis; this fact goes far to strengthen the supposition that the food of both is similar. 2 L. Rutimeyer, /. c. pi. vii. figs. 18, 19. |