It is now generally admitted that these or really the remains of mammalia (although it was at first suggested that they might be reptiles), and the only question open to controversy is limited to this point, whether the fossil mammalia found in the Lower Oolite of Oxfordshire ought to be referred to the marsupial quadrupeds, or to the ordinary placental series. Cuvier had long ago pointed out a peculiarity in the form of the angular process (_c,_ Figs. 342 and 343) of the lower jaw, as a character of the genus _Didelphys_; and Professor Owen has since confirmed the doctrine of its generality in the entire marsupial series. In all these pouched quadrupeds this process is turned inward, as at _c, d,_ Fig. 342, in the Brazilian opossum, whereas in the placental series, as at _c,_ Figs. 340 and 341, there is an almost entire absence of such inflection. The _Tupaia Tana_ of Sumatra has been selected by Mr. Waterhouse for this illustration, because the jaws of that small insectivorous quadruped bear a great resemblance to those of the Stonesfield _Amphitherium._ By clearing away the matrix from the specimen of _Amphitherium Prevostii_ here represented (Fig. 344), Professor Owen ascertained that the angular process (_c_) bent inward in a slighter degree than in any of the known marsupialia; in short, the inflection does not exceed that of the mole or hedgehog. This fact made him doubt whether the _Amphitherium_ might not be an insectivorous placental, although it offered some points of approximation in its osteology to the marsupials, especially to the _Myrmecobius,_ a small insectivorous quadruped of Australia, which has nine molars on each side of the lower jaw, besides a canine and three incisors.[6] Another species of _Amphitherium_ has been found at Stonesfield (Fig. 345), which differs from the former (Fig. 344) principally in being larger. Fig. 340: Part of lower jaw of Tupaia Tana. Fig. 341: Side view of same. Fig. 342: Part of lower jaw of Didelphys Azaræ. Fig. 343: Side view of same. Fig. 344: Amphitherium Prevostii. Fig. 344: Amphitherium Prevostii. Fig. 345: Amphitherium Broderipii. Fig. 346: Phascolotherium Bucklandii. The second mammiferous genus discovered in the same slates was named originally by Mr. Broderip _Didelphys Bucklandi_ (see Fig. 346), and has since been called _Phascolotherium_ by Owen. It manifests a much stronger likeness to the marsupials in the general form of the jaw, and in the extent and position of its inflected angle, while the agreement with the living genus Didelphys in the number of the pre-molar and molar teeth is complete.[7]