The dentition is most abnormal, and permits the division of the Theromorpha into two or three main groups. In the Pareiasauri the teeth of the upper and lower jaws form rather even series of nearly equal size; smaller teeth are carried by the palatal bones. In the Theriodontia the teeth are differentiated in a truly Mammalian fashion into incisors, prominent canines, and multicuspid or tubercular molars. Each tooth, and this applies to all Theromorpha, is implanted in a separate alveolus; _Tritylodon_ only seems to have double-rooted molars. The lower canines cross in front of the upper, just as in Mammals. In _Placodus_, which probably belongs to this assembly, the teeth are few in numbers, very broad and flat, especially those of the palate. In _Dicynodon_ and _Gordonia_ the teeth are restricted to a pair of conical, sometimes very large, tusk-like upper canines, and in _Oudenodon_ the whole mouth is toothless. The configuration of the skull shows two main types. In the Pareiasauri it is completely roofed in by dermal bones, the only holes on the surface being the nostrils, orbits, and the interparietal foramen. The most striking feature of the second type of skull is the tendency to form an almost Mammalian zygomatic arch by the junction of the much elongated squamosal with the jugal bone, both abutting against a downward process of the postfrontal bone. The skull shows a pair of wide supratemporal foramina bordered by the parietals, squamosals, and postfrontals. The composition of the temporal arch varies considerably in detail, and in _Cynognathus crateronotus_ at least there is a small hole within the arch, between the squamosal and jugal, probably the last remnant of the otherwise absent infratemporal foramen. Except in the roofed-in skulls of _Pareiasaurus_ and _Elginia_ there is no separate quadrato-jugal element. The quadrate is firmly fixed by the overlapping squamosal, and the whole pedicle for the support of the mandible is rather elongated, and either stands vertically or slants forwards. The mandible itself is compound. The pterygoids extend backwards so as to approach or reach the {302}distal portion of the quadrate; separate ectopterygoids do not seem to be developed. The shoulder-girdle consists on either side of a large scapula, which is mostly directed obliquely backwards, and is fused with the coracoid; a precoracoid is present or at least indicated by a notch or foramen; it is usually fused with the other bones. At least some genera possess a T-shaped interclavicle and clavicles; _Pareiasaurus_ possesses also a pair of cleithra.