long under the orbit and the remainder, _i.e._, its connection with the jugal canal, is restored (fig. 22, G). There is, nothing unusual to be observed in that portion of the infraorbital canal which is preserved. The supraorbital canal is indicated by a curved, broad, shallow groove on the inner side of each orbit. As stated above, there seems to be a connection between this canal and the temporal, but I am not sure. The primitive conditions shown in the lateral-line canals in _Erpetosaurus tabulatus_ Cope are the presence of the occipital cross-commissure and the ring-like formation of the temporal and jugal canals, which is too clearly indicated to be overlooked. Measurements of the Type of Erpetosaurus tabulatus Cope. mm. Median length of skull 29 Width of skull, posterior border, estimated 37 Width between tabulare angles 18 Length of orbit 8 Width of orbit 6.5 Diameter of nostril 1 Diameter of pineal foramen 1 Length of right clavicle 13 Width of right clavicle 5.5 Mandible Provisionally Associated With Erpetosaurus tabulatus Cope. Moodie, Bull. Amer. Mus. Nat. Hist., XXVI, pp. 351-352, pl. lix, fig. 2; pl. lxiv, fig. 3, 1909. This specimen is preserved almost completely on a slab of soft coal. It is impossible to determine positively to what microsaurian species the mandible belongs, but it may, for the present, be associated with _Erpetosaurus tabulatus_ Cope on account of its size and the character of its sculpture. This is the first and almost the only known example of a mandible of an American microsaurian. The form of the jaw is perfectly preserved, although the condition of the articular surface can not be determined.