The form of the impression of the mandible in the present specimen is unlike anything known to the writer among other Carboniferous or later Amphibia. The rami are long, slender, deep, slightly curved, and pointed anteriorly. The anterior symphysis was not a complete sutural union, but was occupied partly by cartilage or other connective tissue. There are no definite traces of the appendicular skeleton. The traces of the body (fig. 15, A) indicate an elongated, rather slender animal, but further than this nothing can be said in regard to its structure. The occurrence of a typically caudate form in the Carboniferous is unusual and complicates still further our understanding of the origin and relationships of the early Amphibia. Measurements of the Type. mm. Length of entire impression 50 Length of mandible along median line 10 Width of mandibular ramus 9 Length of basibranchial 2.5 Width of basibranchial 0.75 Length of hypohyal 2.4 Width of hypohyal 1.5 =Genus HYPHASMA Cope, 1875.= Cope, Proc. Acad. Sci. Phil., p. 16, 1875. Cope, Geol. Surv. Ohio, II, pt. II, p. 387, 1875. Type: _Hyphasma lævis_ Cope. "Vertebræ osseous, the posterior dorsals, and probably the caudals, furnished with fan-like neural spines; limbs unknown--(?) wanting. Thoracic shields present. Ventral armature, consisting of rhomboidal scuta, forming packed rows arranged in chevrons, directed backwards, on top of which are the usual rod-like scales arranged in packed chevrons, with the angle directed forward. "The general appearance of the type of this genus is that of a Ptyonius, but the ventral armature is different from anything observed in the known genera of this group. The larger external scuta are like those of the species of Colosteus (Sauropleura), but their series have a different direction. The inner chevrons are those of many other genera" (123). =Hyphasma lævis Cope.= Cope, Proc. Acad. Sci. Phil., p. 16, 1875. Cope, Geol. Surv. Ohio., 11, pt. II, p. 387, pl. 37, fig. 4, 1875. Type: Specimen No. 9023 (in counterpart), American Museum of Natural History. Horizon and locality: Linton, Ohio, Coal Measures.