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Show 1870.] PROF. W. H. FLOWER ON JELURUS FULGENS. 767 CONCLUSION. With reference to the skeleton, I must content myself on the present occasion with noting that the vertebral formula is C. 7, D. 14, L. 6, S. 3, C. 18*, that there is no trace of a clavicle, and that the humerus has a supracondylar perforation. It will be seen from the foregoing notes that, in all essential points of its structure, Mlurus conforms to the other arctoid or bear-like carnivora, a group comprising the Ursidae, Procyonidce, and the Mus-telidee. T h e question remains whether it can be included in either of those three families, or whether it must constitute a familv for itself. In the structure of the viscera, the minor modifications from the general type characteristic of the section have not yet been studied with sufficient attention, or in a sufficient series of species, to be made use of in dividing the families or genera. This, however, is a subject to which the attention of systematic zoologists will naturally be more closely directed when the consideration of the external and more easily accessible characters becomes exhausted, or fails to supply the required information. In the mean time, the dental characters, and more especially the number and form of the true molars, are generally relied on as, at all events, the most convenient for diagnosis. All the known Ursida? have f- of these teeth on each side, all the known Procyonidce -§, and all the known Mustelidee \, or in one case but -j-. The Ursidae are characterized by the greatest development of the molar series backwards ; for not only is there an additional molar in the lower jaw, wanting in all the other forms, but the posterior molar in the upper jaw is a very large tooth ; and in all the most typical, or, rather, most specialized, Bears (Ursus proper) it is actually longer from before backwards than the tooth in front of it. In Melursus, and the section of Ursus called Helarctos, this tooth is scarcely, if at all, longer than the one in front of it; and the same is the case in the very generalized extinct Hycenarctos. In the Procyonida?, on the other hand, it is always smaller than the tooth in front of it, thus indicating a transition to the condition of total absence met with in all the Mustelidee. The existing Ursidee also differ, not only from the Procyonidce, but from all other Carnivora, in the structure of the last upper premolar, or "sectorial tooth" of the more typical members of the order. This tooth usually consists essentially of a more or less compressed and cuspidated " blade " supported on two roots, and an inner lobe (almost always near the anterior end of the blade) supported by a distinct root. In the Ursidae alone the third root is wanting, and the inner lobe is either absent or quite at the posterior end of the blade, supported on a thickening of the posterior rootf. * Hodgson gives thirteen dorsal and five lumbar vertebra;, but states that he had not a perfect skeleton by him to refer to while writing. t In a specimen of Melursus labiatus in the Museum of the Royal College of Surgeons there is a small third root on the inner side of the last upper premolar, but this is confined to the tooth of one side of the jaw only. |