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Show 73 and, like them, has a band of enamel extending along the superior tusks, aud a much produced symphysis of the mandible, from which two smaller tusks project. The posterior- inferior molar supports five transverse series of tubercles, bf which the posterior is less developed than the others. Each series is composed of two cusps of a conic form, which are separated deeply from each other, and are not united at the base so as to become confluent on attrition. The cones of the outer side support one or two accessory tubercles on a line with their inner or median face, so that the transverse section of a worn tooth with the two accessory cusps is that of a trefoil with the lobes inward. The penultimate molar in the same jaw supports three transverse series. The symphysis is elongate, depressed, and subspatulate; its proximal half is excavated; the distal half flattened. Two tusks project from the extremity; they are short, obtuse, and flattened on the inner side. Total length of a specimen which in entire from the end of the symphyseal tusks to just behind the last molar, 29 inches: length to first molar, ( penultimate,) 19 inches; length of first molar, 4.25 inches; of lust molar, 6.5 iuohes; width of same, 3 inches; width across the rami at end of last molar, 18 inches; width between anterior borders of first molar, 2.5 inches; width of symphyseal spout, least, 4.5 inches; at base, tusks, 4.75 inches; length of free portion of symphyseal tusks, 4 inches; diameter of symphyseal tusks, 1.75 inches. The North American mastodons are referable to two groups, characterized by the structure of their molar teeth. In the first, the cross- crests are divided by a fissure only, the other by the transverse series of two or more deeply separated tubercles. To the first belong Af. ohioticus, Cuv., and At. proavuB, Cope; to the second, M. Chapmanii, Hays, ( from which M. obscurus could not be at present distinguished ;) if. Skepardii, Leidy : M. andium, D'Orb., ( the last two referred by Leidy to M. obacurus;) M. mirificus, Leidy, ( closely allied to M. Humboldtii /) and M. product ™ , Cope. No question as to the distinctness of the M. productus could arise, although onr knowledge of the M. Chapmanii, to which it has been referred, is very slight. As described by Drs. Hays and Leidy, the lateral tubercles of the molars in that species are closely appressed or not separated; beiug sometimes continuous across the crown of the tooth. This description applies to one of the specimens ( a cast) seleeted by Dr. Leidy as his type, and to a second specimen referred by him to the M. andium. The second type- specimen of Dr. Leidy, a fragment of a posterior molar, is undistinguishable from corresponding parts of M. andium. The M. Skepardii, as described by Leidy, is evidently quite, distinct from both the preceding and from the M. productus, in the absence of accessory tubercles of the lateral principal cusps of the molars. The specimens are chiefly from the east side of the Rio Grande; but a few were obtained near Santa Clara on the western side. RODENTIA. Panolax savctafidei, Cope, Report on Vertebrate Fossils of New Mexico, Annual Report Chief of Engineers, 1874, p. 605. Eumys loxodon, Cope, loc. cit., p. 605. This rat is represented by a mandibular ramus containing all of the teeth. These are identical in essential structure with those of the Eumys elegans, and the species is therefore provisionally referred to that genus. I originally described it as a Hesperomys, a genus to which it is also closely related so far as the preserved portions indicate. Steneofiber pansus, Cope, Proceedings of the Philadelphia Academy, 1874,22. The molar teeth exhibit a regular gradation in width from the large anterior to the small posterior. In the mandibular series the second and third are broader than long; the first and fourth longer than broad, and with an angle on the outer anterior side of the crown. There is an inflection or groove of the enamel on both inner and outer sides of the crown, and one enamel- area before and one behind them on all excepting the last molar, where there are two in front. First nearly twice as large as last molar. Lower incisor with smooth enamel, and angulate on the extero- anterior border. Ramus stout. Length of molar series, 0m. 016; length of first molar, 0m. 005; width of first molar, 0m. 004; width of last molar, 0m. 0035; transverse diameter of incisor, 0m. 004; depth of ramus, 2 ™ . 012. The regular diminution of the size of the teeth from front to rear is characteristic of this species according to Dr. Leidy; their reduction in size in the 8. Nebrascensis is more abrupt. The latter species is said to be of Miocene age. AVES. Vullur umbrosus, Cope.- Cathartes umbrosus, Cope, Report on Vertebrate Fossils of New Mexico, Annual Report Chief of Engineers, 1874, p. 606. The elongate beak and weak toes of this genus resemble those of tin vulturine types, and the absence of any indication of nasal septum at the fractured base of the L L - r > |