mm. Length of portion of vertebral column preserved 7 Width of ventral armature 18 Length of a vertebra 9 Width of same vertebra 4 CHAPTER XX. THE MICROSAURIAN FAMILY MOLGOPHIDÆ, FROM THE COAL MEASURES OF OHIO AND MAZON CREEK, ILLINOIS. =Family MOLGOPHIDÆ Cope, 1875.= Cope, Geol. Surv. Ohio, II, pt. II, p. 157, 1875. Cope, Bull. U. S. Nat. Mus., No. 1, p. II, 1875. Type of family: _Molgophis_. Body long, serpentine, a few species apparently limbless, ribless, and with abdominal armature lacking. Vertebræ elongate, neural and hæmal spines short or absent. Ribs long, heavy, and broad. The vertebræ seem to bear the characteristic marks of the family. One species has the skeleton reduced to a lanceolate skull and a string of about 50 slender vertebræ, all the rest of the skeleton being absent. The family is very poorly known, but was apparently of wide distribution in North America and confined to this continent. The representatives of the group are known from Iowa, Illinois, and Ohio. Four genera are assigned to the family, but future discoveries will undoubtedly demand revision of the present classification. The genera are _Molgophis_, _Pleuroptyx_, _Phlegethontia_, and _Erpetobrachium_. The distinguishing characters of these genera are apparent from the descriptions of the various forms. The skeletons of the species are too incompletely known to allow the establishment of a tabular key to the genera. =Genus MOLGOPHIS Cope, 1868.= Cope, Proc. Phila. Acad. Nat. Sci., p. 220, 1868. Cope, Trans. Amer. Phil. Soc., XIV, p. 20, 1869. Cope, Geol. Surv. Ohio, II, pt. II, p. 368, 1875. Cope, Trans. Amer. Phil. Soc., XV, p. 263, 1874. Type: _Molgophis macrurus_ Cope. Cope (123) gives the following: "The characters of this genus are: body long, serpentine, without dermal armature, so far as known; vertebræ long and broad, with very prominent zygapophyses and moderate neural spines; ribs large, curved. No limbs or cranium can be ascribed to the type of the genus. The ribs are long, and though the head is not bifurcate, there appears to be both tubercle and head on the dilated extremity. Where crushed they display a large median vacuity. "This genus differs from Ophiderpeton Huxley (334) in the characters of the dorsal vertebræ, which, in their projecting zygapophyses, resemble those of Amphiuma. The lack of ventral armature distinguishes it from _Œstocephalus_, while its well-developed ribs separate it from _Phlegethontia_." =Molgophis macrurus Cope.= Cope, Proc. Phila. Acad. Nat. Sci., p. 220, 1868. Wyman, Am. Jour. Sci. and Arts, p. II, fig. 1, 1858 (refers to a batrachian reptile). Cope. Trans. Amer. Phil. Soc., XIV, p. 20, 1869. Cope, Trans. Amer. Phil. Soc., XV, p. 263, 1874.