This is one of the most interesting genera of the present series. It rests chiefly on a single specimen of one species, which is not perfect, but which displays the following characters: Head elongate-triangular; body and tail extremely elongate, the dorsal vertebræ without ribs, and the caudals without dilated spines; no ventral armature nor limbs. As a great portion of the length is presented, and no ventral rods or scales are visible, and as this character is confirmed by a second specimen, it probably belongs to the genus. The pectoral shields are also wanting in the specimen, but as there is a considerable vacuity behind the skull of the specimen, it may be that these were lost with other parts. Chevron bones are not observable on the caudal vertebræ. This form is a true amphibian snake. =Phlegethontia linearis Cope.= Cope, Geol. Surv. Ohio, II, pt. II, p. 367, pl. xliii, fig. 2, 1875. Type: Specimen in the American Museum of Natural History. Horizon and locality: Linton, Ohio, Coal Measures. In the only specimen the dorsal vertebræ are much involved anteriorly, so that the length is not readily ascertained. There is an outline of a triangular object which may represent the skull of this specimen, although it is so far removed from the vertebræ that there is some doubt as to whether it belongs with the vertebræ or not. Indeed, there is even doubt whether it is a skull. The vertebræ have longitudinal diapophysial keels, and have a zigzag interlocking of neural arches. The latter are distinctly turned outward. The vertebræ are very numerous, and the tail very attenuated. The number preserved is about 60. The total length of the coils unwound is about 295 mm., or 11 coils in 8 lines; but there are interruptions not measured and confusions not unraveled. This is the most elongate and slender of all the species of the Carboniferous Amphibia. The vertebræ are apparently ribless and there are no evidences of limbs or pectoral plates. It may be said that the body consists entirely of skull and vertebræ. Measurements of the Type of Phlegethontia linearis Cope. Entire length of skull (?) 18 mm. Width of same 8 mm. Length of vertebral column as preserved 295 mm. Length of single vertebra 2.50 mm. Height of vertebra 1.50 mm. Estimated length of body 15 in. No. 8370 G, American Museum of Natural History, shows a few vertebræ. =Phlegethontia serpens Cope.= Cope, Geol. Surv. Ohio, II, pt. II, p. 367, pl. 32, fig. 2, 1875. Type: Specimen No. 1102 G, American Museum of Natural History. Horizon and locality: Linton, Ohio, Coal Measures.