mm. Length of the skull along median line (estimated) 60 Length from muzzle to quadrate angle 71 Width at posterior border 69 Width at orbits 40 Length of orbit 9 Width of orbit 8 Interorbital width 8 Length of nostrils 2 Measurements of Another Specimen of the Species. (No. 8598 G, American Museum of Natural History.) mm. Median length of skull 56 Length to quadrate angle 61 Width at posterior border 50 Length of orbit 7 Width of orbit 6 Interorbital width 4.5 The specimens of this species were collected by Dr. J. S. Newberry. Erpetosaurus obtusus Cope, 1868. Cope, Proc. Phil. Acad. Nat. Sci., 1868, p. 213. Cope, Trans. Amer. Phil. Soc., XIV, p. 12, fig. 1, 1869. Cope, Geol. Surv. Ohio, II, pt. II, p. 396, fig. 11, 1875. Cope, Proc. Amer. Phil. Soc., 1885, XXII, p. 407 (Pal. Bull. 40). Moodie, Bull. Amer. Mus. Nat. Hist., XXVI, p. 350, pl. lx, fig. 2. Type: Specimen No. 8601 G, American Museum of Natural History. Horizon and locality: Linton, Ohio, Coal Measures. The species, _Tuditanus obtusus_, was first described by Professor Cope as _Dendrerpeton obtusum_, but he subsequently referred the species to the genus _Tuditanus_. It was removed by the writer to the genus _Erpetosaurus_ in 1909. The species is known from two partially preserved crania. The skull elements seem to have disappeared and left only the impressions. The sutures are, for the most part, clearly represented, but the skull shows no sculpturing. On the posterior third of one cranium there is a small space which seems to be slightly sculptured, as Cope indicated in his drawing. The general form of the skull is that of a broad oval, truncate posteriorly. The orbits lie in the anterior third of the skull, and the pineal foramen in the posterior third. Cope compared the skull to that of Huxley's _Erpetocephalus_, to which it has some resemblance. The nostrils are elongate and are situated at an obtuse angle with relation to the main axis of the skull.