[Illustration: FIG. 29.—Inner view of the right ramus of the mandible of _Phascolotherium bucklandi_; from the Stonesfield Slate. The outline shows the natural size. _i_, Incisors (one missing); _c_, canine; _p_, premolars; _m_, molars. The mylohyoid groove is seen near the lower border. (After Owen.)] [Illustration: FIG. 30.—Reversed inner view of the left ramus of the mandible of _Amphilestes broderipi_; from the Stonesfield Slate. Twice natural size. The restoration of the anterior teeth is conjectural, and the condyle is placed too high. (After Owen.)] The last type of molar dentition occurring among the Mesozoic Mammalia is that found in the lower jaws (Fig. 31), upon which the genus _Spalacotherium_ was established, the upper jaws, described as _Peralestes_, being apparently referable to the same animal. Upper and lower teeth of this form are represented in Fig. 4 (6, 7), p. 31, where they are described as typical examples of the tritubercular type of molars, the upper teeth having one inner and two outer cusps, and the reverse condition obtaining in the lower ones. This type of molar presents a marked resemblance to that found in the existing Insectivorous genus _Chrysochloris_; the number of lower teeth in _Spalacotherium_ is, however, _i_ 3, _c_ 1, _p_ + _m_ 10, by which it is widely distinguished from all the Insectivora. _Menacodon_, of the Upper Jurassic of the United States, appears to be allied to _Spalacotherium_. [Illustration: FIG. 31.—Part of the left ramus of the mandible, viewed from the outer side, of _Spalacotherium tricuspidens_; from the Purbeck of Swanage. Twice natural size. (After Owen.)]