Horizon and locality: Coal formation at the South Joggins, Nova Scotia. Fragments of 3 specimens from 3 trees represent this species (plate 10). It seems to have been of stouter build than _H. lyelli_, with the limbs shorter in proportion. Its generic affinities are somewhat doubtful, as it presents in some respects characters intermediate between _Hylonomus_ and _Hylerpeton_. Mandibular and maxillary teeth broadly conical, about 20 in each mandible 3 in 1 mm.; anterior mandibular teeth somewhat larger than the others, and bent or hooked. Vomer or palate with minute teeth. Thoracic plate large. Scales of abdomen oval, but somewhat narrow, and tending to be oat-shaped. Length of mandible (imperfect) mm. 9 Length of humerus mm. 7 Length of vertebra mm. 2 Length of tibia (?) mm. 5 Length of thoracic plate cm. 1 Length of six caudal vertebræ mm. 8 =Hylonomus multidens Dawson.= Dawson, Phil. Trans. Roy. Soc. London, 1882, pt. H, p. 637, pl. 39, figs. 23-26. Dawson, Proc. and Trans. Roy. Soc. Canada, 1895, p. 74 Type: Specimen No. 3061-2, Peter Redpath Museum, McGill University. Horizon and locality: Coal formation at the South Joggins, Nova Scotia. This animal is known only by portions of bones of the head and a few other fragments. The scattered bones of the extremities are inseparable from those of _H. lyelli_ occurring with it. As compared with that species, the bones of this are smoother and more delicate. The teeth are more numerous and slender. The crushed distal end of a femur or humerus found near the skull indicates that the limbs were well developed. mm. Length of mandible 11 length of skull 15 Length of femur 9 Teeth, 5 to 6 in 1 mm. =Hylonomus wymani Dawson.= Dawson, Quart. Jour. Geol. Soc. London, XVI, p. 277, figs. 27-29, 1860. Dawson, Air-breathers of the Coal Period, p. 52, 1863. Dawson, Phil. Trans. Roy. Soc. London, 1882, pt. II, p. 637, plate 39, figs. 15-17. Dawson, Acadian Geology, 3d ed., p. 378. Type: Specimen No. 3061, Peter Redpath Museum, McGill University. There is also specimen No. R 446 in the British Museum (393, pt. IV, p. 224). Horizon and locality: Coal formation at the South Joggins, Nova Scotia. As compared with the _H. lyelli_ the present species is smaller in size, more elongated in form, had the teeth less numerous (about 22 in the mandible), and shorter and more obtuse in form. There are 6 to 7 in I mm. This species is much more rare than _H. lyelli_, but quantities of minute bones, probably belonging to it, occur in the coprolitic matter. In one specimen 38 vertebræ of this species were found partially associated, indicating along, slender body. The body is covered with scales and ventral scutellæ are present. Dawson questions whether this species may not be the young of _H. lyelli_.