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Show 114 MR. OLDFIELD THOMAS ON [Feb. 18, external margin of the blade, so that a valley is formed between the inner and the outer part of the tooth. By the conformation of its upper carnassial, therefore, the fossil is excluded from the Melince-the upper and the lower one making only a slight approach towards the form they have in some members of this subfamily ; whilst the characters of the skull and of the skeleton, so far as known, bring it likewise in closer connection with the Mustelince and with Mustela in particular. To emphasize this, it seems preferable to leave it in the latter genus, viz., to revive the name by which it was originally described- Mustela palieaitica Weith. EXPLANATION OF PLATE VII. Skull of Mustela palceattica Weith., from Pikermi; Geological Museum, Turin. All figures of the natural size. Fig. 1. Side view. Fig. 2. Upper view. Fig. 3. Lower view. Fig. 4. Posterior upper premolar and molars, right side. Fig. 5. Lower true molars and posterior premolar, right side. 2. On Two new Genera of Rodents from the Highlands of Bolivia. By OLDFIELD THOMAS, F.R.S. [Received January 28, 1902.] (Plates VIII. & IX.1) Mr. Perry 0. Simons, the collector who has been doing such admirable work in the Andean chain, and to whose efforts we owe the discovery of a very large number of the mammals of that interesting region, has now sent home a collection from the high grounds of South-western Bolivia, from the Departments of Oruro, Potosi, and Sucre. Among these, besides some new species of known genera, described elsewhere, there are examples of two rodents so distinct as to demand generic separation, and I have therefore thought them worthy of being brought before the Society for description and illustration. NEOCTODON, gen. nov. (Octodontkhe.) Tail comparatively bushy. Palms and soles granulated, the pads imperceptible. Palatal foramina longer than in Octodon, the actual openings, instead of only the outer fossa, penetrating into the maxilla?. Incisors smooth, comparatively thick antero-posteriorly, their depth rather more than 1| their breadth, as compared with about lg in Octodon. Molars rootless, simpler than in Octodon, with a slight concavity on their outer side and none on the inner, there being no trace 1 For explanation of the Plates, see p. 117, |