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Show 1893.] DR. C. J. EORSTTH MAJOR ON MIOCENE SQUIRRELS. 191 Sc. spermophilinus is represented by a fragment of the left maxilla (Plate X . fig. 4), carrying the posterior premolar and the two anterior molars, and by several mandibular rami (Plate X. figs. 6-9). A minute alveolus for p., is visible in front of the posterior upper premolar. The inferior molars show the cup- or basin-shaped conformation, the cusps being arranged laterally. Deperet is of opinion that the molars of Sc. spermophilinus differ from Sc. vulgaris only in small particulars. I find more resemblance to some Oriental members of the subgenus Sciurus ; the antero-internal cusp of the lower molars being extremely elevated, whilst the postero-internal cusp is almost suppressed (Plate X . fig. 9). W e meet with exactly the same pattern in the Oriental Sc, atrodorsalis, Gr., Sc.rosenbergi, Jent., Sc. caniceps, Or., Sc. brookei, Thos., and others. The third lower molar is more elongate than in Sc vulgaris; this, too, is a character of the Oriental group of Squirrels mentioned. Besides, both upper and lower incisors are vertically striated by ridges (Plate X . fig. 5). Amongst recent Sciurinee, only Rhithrosciurus, whose molars, however, are very different from those of the fossil, presents this character. It occurs also on lower incisors of some species of Sciuroides from Cailux, in the British Museum. As the same striation of incisors is found in the Tillodont Ccdamodon of the Lower AmericanJ and Swiss2 Eocene, it may prove to be an inherited character. Length of m2, mv px sup., G millim.; length of m3, m2, n^, p. inf., 7'5 millim. Xerus grivensis, n. sp. (Plate X . figs. 2, 3).-A left mandibular ramus, showing the three molars and the alveolus of the premolar. Length of the three molars 6 millim. Incisor without vertical ridges. The molars present a more advanced stage of lophodontism than those of Sc, spermophilinus, not only the anterior cusps uniting transversely, but the postero-external and postero-internal cusp-the latter more fully developed than in Sc. spermophilinus-showing the same tendency. So that we have three, instead of two, transverse valleys, the median and posterior valley being incompletely divided. I could not better characterize the molars of this fossil than by calling them a minute and somewhat less semi-hypsodont form of X. berdmorei, Bly., from Martaban, Tenasserim, Cambodja, and Cochin-China. Sciuropterus albanensis, n. sp.-The third fossil, a left ramus of the lower jaw (Plate X. fig. 1, Plate X I . figs. 3-5), is strikingly similar in the character of the molars and the ramus to some of the larger species of Sciuropterus, and especially to Pteromys tephro-melas, Giinth.3 (Plate X I . figs. 1, 2), and Pter. phceomelas, Giinth., 1 E. D. Cope, " The Vertebrata of the Tertiary Formations of the West," Book I. 1883 (Rep. Un. States Geol. Surv. of the Territ. vol. iii., Washington, 1884) pp. 188-192, pi. xxiv.c. fig. 1 b. 2 L. Riitimeyer, " Die Eocane Saugethierwelt von Egerkingen " (Ziirich, 1891), pi. viii. figs. 25-27, p. 126. 3 Proc. Zool. Soc. Lond. 1873, p. 413, 1886, p. 53. |