Skull with the palatines situated near the middle line, internally to the vomers and pterygoids, and the palatine vacuities small and placed far back. Vertebræ (_Ichthyerpeton_) discoidal. Teeth less complex than in the Anthracosauridæ. A ventral armor present and the entire body covered with small cycloid imbriated scales. The type genus of this family was placed by Fritsch (251) with the Archegosauridæ, although its resemblance to _Anthracosaurus_ was pointed out; it was subsequently made the type of a family by Lydekker (393) in 1890, and placed next the Archegosauridæ. Known from the Coal Measures of Bohemia, Ireland, and Ohio. Two genera from North America, _Ichthyerpeton_ and _Cercariomorphis_, are assigned tentatively to this family, both known from the Coal Measures (462) of Linton, Ohio, and both with the body completely scaled. The distinguishing characters are found chiefly in the shape and arrangement of the scales, the structure, form, and size of the body, all of which are given full treatment in the discussion below. =Genus ICHTHYERPETON Huxley, 1866.= Huxley, Trans. Roy. Irish Acad., XXIV, p. 195, pl. xxiii, fig. 1; Scientific Memoirs, III, p. 195, pl. 23, fig. 1, 1866. The genus was founded by Huxley (334) for the reception of the species _Ichthyerpeton bradleyæ_ from the Kilkenny Coal Measures of Ireland. The remains of the type specimen represent "the hinder moiety of the trunk, with the greater part of the tail, of an animal whose scaly integument and laterally compressed, fin-like tail might easily lead one to take it for a fish, were not its true position among higher vertebrata settled at once by the digitate hind limb; while its alliance with the labyrinthodonts is indicated by the delicate spicular ossicles, which form a rudimentary dermal shield along the belly." (Huxley.) =Ichthyerpeton squamosum Moodie.= Moodie, Jour. Geol., XVII, No. 1, p. 69, 1909. Moodie, Proc. U. S. Nat. Mus., 37, p. 24, 1909. Type: Specimens Nos. 4476 and 4459, U. S. National Museum. Locality and horizon: Linton, Ohio, Coal Measures. The present species is based on well-preserved remains from the Linton, Ohio, beds. There are two specimens of the species preserved on blocks of coal and together they represent the greater part of the length of the animal. The species is located in the genus Ichthyerpeton, which was founded by Huxley (334, p. 351) on remains from the Coal Measures of Ireland, on account of the character of the dermal covering, which consists of small scales such as Huxley described in the form from Ireland. The specific characters of this form are the small size of the rounded scales, the attenuated tail, the apparent absence of limbs, the character of the ventral scutellation, and the slightly curved condition of the ribs.