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.
This amphibian is much larger than the last, approaching nearly in its dimensions the Molgophis macrurus. It is represented by a series of 22 vertebræ, which, like those of Phlegethontia linearis, are devoid of ribs, abdominal armature, dilated neural spines, etc. The series when complete must have been very long, as there is little difference in size between the first and the last of the 22. They are marginate fore and aft, and much contracted medially, owing to the transverse expanse of the diapophyses. There may be, indeed, a diapophysial element beneath these, but, if so, the two are indistinguishable. They are connected by longitudinal impressions, indicating the existence of the tendinous bands in the longitudinal muscles seen in Amphiuma, or the osseous spicules seen in the same situation in birds. The neural spines, as indicated by their narrow bases, occupy the length of the neural arch, and remind one of Amphiuma. Width of one of the vertebræ, 3 lines.