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. CHAPTER XXI. THE MICROSAURIAN FAMILY SAUROPLEURIDÆ, FROM THE COAL MEASURES OF OHIO. =Family SAUROPLEURIDÆ Hay, 1902.= Hay, Bull. U. S. Geol. Surv., No. 179, p. 419, 1902. The present family is an association of related forms due to similar structure of vertebræ, ribs, ventral scutellation, and limbs. There is no character in the skull which would indicate a separation of the genera here included, at least in the light of present knowledge. The family may be characterized as: Subaquatic or terrestrial vertebrates with a typically amphibian development of the ventral armature; ribs intercentral, as in all members of the order; skull elongate and slender or broad and obtuse; cranial and dermal elements of the pectoral girdle sculptured; lateral-line canals indicated in one genus, Saurerpeton; limbs well developed, with well-developed digits and ungual phalanges claw-like; body usually slender, broad in Saurerpeton; the ribs broad and heavy; the vertebræ relatively stout; ventral armature highly developed, reaching the height of specialization among the Microsauria; scutellæ consisting of rods, plates, or stout bristles. The family is represented by 5 genera: _Sauropleura_, _Saurerpeton_, _Ctenerpeton_, _Leptophractus_, and _Eurythorax_, the association of the last two genera being provisional. The genera may be distinguished as follows: I. Pectoral elements sculptured, clavicles triangular, interclavicle diamond-shaped, ventral scutellæ rods, arranged _en chevron_ with anterior angle _Sauropleura_ II. Pectoral elements slightly sculptured, cranium broad, obtuse and sculptured, ventral armature broad imbricated plates extending on to the throat _Saurerpeton_