Considering the age of these little creatures and their low position in the reptilian scale–in fact, they stand almost as low {289}as the Proreptilia–it is not to be wondered at that they still retain a number of amphibian features. The skull is encased in dermal bones as in the Stegocephali, and the dermal armour of the trunk and tail is composed of many bony, sculptured scales, which cover back, sides, and under surface. The middle rows on the back are the largest, while the scales on the belly are arranged in transverse rows, which imbricate and converge obliquely headwards. Special gular plates seem to be absent. The skull has an interparietal foramen. The jaws and the palate are furnished with small, simple teeth, and there is a large parasphenoid bone, an eminently amphibian character. The occipital condylar articulation is supposed to be double. The centra of the vertebrae are deeply amphicoelous, elongated, and constricted in the middle, just like those of the Aistopoda and Branchiosauri. The dorsal spinous processes are strongly developed, and with the zygapophyses are very reptilian. Transverse processes are absent or very short, the tubercular portions of the ribs articulating with the centra, the capitula mostly intervertebrally, in any case close to the anterior end of the centra. The tail-vertebrae possess very typical, movable chevrons, placed intervertebrally, and bear an extraordinary resemblance to those of Geckos. The ribs are long and slender, but there is no sternum. The fore- and hind-limbs are pentadactyle, in opposition to the invariably four-fingered Stegocephali. The shoulder-girdle consists of scapulae, coracoids, clavicles, cleithra, and a T-shaped interclavicle. The pelvis also resembles that of certain Stegocephali by the separately ossified, somewhat disc-shaped, flat ischia and pubes, which seem to have been joined together by cartilage into one broad mass. _Hylonomus_, Dawson's type of Microsauri, was found in the Coal-measures of Nova Scotia, within decayed tree-stumps. Closely allied, if not identical, but much better known is _Hyloplesion_, e.g. _H. longicostatum_ of the uppermost Permian of Nyrschan in Bohemia. Total length under 4 inches; eyes with bony sclerotic rings; neck short. The truly Permian genera _Dawsonia_, _Melanerpeton_, _Orthocosta_, and _Seeleya_ are allied forms, the last scarcely one inch in length, but well preserved. _Petrobates_ of the Triassic Lower Red Sandstone of Saxony has an arrangement of the ventral dermal armour closely resembling abdominal ribs. {290}ORDER II. PROSAURI Mostly extinct, chiefly Permian and Triassic, terrestrial, unarmoured reptiles with deeply biconcave vertebrae, numerous intercentra and chevron-bones, fixed quadrates, complete pentadactyle limbs and shoulder-girdle, entepicondylar foramina, acrodont teeth, and many small abdominal ossifications.