The form of the skull of _Amphibamus grandiceps_ Cope is not unlike that of _Tuditanus minimus_ Moodie (462) from the Linton, Ohio, beds, but it is less acuminate than in that form. The large size of the orbits is especially striking. The shape of the skull is triangular, with concavities in the posterior table which correspond to the ear-slits so characteristic of _Metoposaurus_ (242) from the Keuper of Germany. The narrowed posterior table of the skull is truncate, as in several other genera of Microsauria, notably _Tuditanus_ and _Saurerpeton_. In structure the skull differs but little from many of the other Carboniferous forms, but the arrangement of the elements of the skull is more regular than in other genera. The premaxillaries are very small elements in the anterior tip of the skull. They border the nares. The skull is rather peculiar among the Microsauria in the possession of a distinct lacrimal. I have detected this element in the cranium of _Stegops divaricata_ Cope. As here defined the lacrimal is triangular, with its posterior border formed exclusively by the prefrontal. Its other relations are the normal ones. The nasal is elongate, with the usual relations of that element. The frontal is slightly longer and broader than the nasal. It apparently forms a portion of the inner border of the orbit. The parietal foramen lies in the anterior fourth of the parietal, a rather unusual position for this structure. The parietals, as in so many of the Microsauria, together form the largest element of the skull and are roughly a triangular area in the postero-median portion of the skull. The postparietal and the tabulare are clearly distinguishable and they have the usual relations for those elements. The maxillary, jugal, and quadratojugal together form the greater part of the maxillary border. The postero-lateral angle of the skull is, as visual, formed by the squamosal. The orbit is bounded posteriorly by the postorbital and the postfrontal, which include in the angle between them the quadrangular squamosal. The orbit is especially remarkable for its size as compared with the dimensions of the skull, being without a parallel among other known Microsauria. Around the border of the orbit in the specimen Cope studied (105) there were found 14 quadrangular plates which he called "superciliary plates." Hay (316) was inclined to regard them as sclerotic plates. In the Yale Museum specimen (plate 4, figs. 5, 6) there are 20 of these plates, and there seems to be no doubt that they are sclerotic elements. In the restoration (fig. 26) 29 sclerotic plates are given, but there is no assurance that this number is the exact one. They may also have been slightly larger, but not as large as in Branchiosaurus.