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Show 358 PROF. OWEN ON A NEW SPECIES OF STHENURUS. [Apr. 17, it is with the characters of the long trenchant premolars, the retained canines, the produced anterior incisors, and the palatal vacuities, an addition to those eA-ideuces of the departure of the genus from Macropus proper and Sthenurus, and of its approximation to Hypsiprymnus. It may be that the grounds of m y homologies of the teeth of Maeropodidae are not deemed conclusive. They are as follows, and I am open to any objections which may have barred Prof. Garrod's acceptance of them. In the subjoined cut, A represents the dental series, deciduous and permanent, exposed in the right mandibular ramus of a young Pig (Sus scrofa, h.); B represents the same in a young Kangaroo (Macropus major, Shaw). In place of the incisors di 1, di 2, di 3, and of the canines, c, in the Pig (A), we have the single incisor, i, in the Kangaroo (B), which may be the homologue of i 1 in the Pig. Of the tooth d 1 in the Pig there is no homologue in the Kangaroo. The small foremost molar, d 2, in the Kangaroo, I view as the homologue of d 2 in the Pig; but in the Pig there is a vertical successor, p 2, which is not developed in the Kangaroo. The tooth cl 3 in the Kangaroo is the homologue of d 3 in the Pig : in both it has a vertical successor-a true ' premolar,' p s, which displaces it usually, in Macropus major, a short time after the fall of «?2 ; and this premolar rises into place, like p 3 in the Pig, without displacing the tooth d 4. Beneath d 4, in the Kangaroo, there is no vertical successor-nop4 as in the Pig; and in this respect di in the Kangaroo resembles d2. These homologies being determined, or accepted, those of m 1, m 2, m 3, with the molars similarly symbolized in the Pig, follow as a matter of |