Page:Synopsis of the Exinct Batrachia and Reptilia of North America. Part 1..pdf/14

 10 THE EXTINCT BATRACHIA, REPTILIA PARIOSTEGUS, Cope. Proceed. Acad. Nat. Sci. 1863, p. 211. This genus is represented by a large part of the cranium of a batrachian from the triassic coal measures of Chatham county, North Carolina. If not a batrachian, it could only belong to a Ganoid fish, but though sonic of its characters are somewhat ichthyic, it lacks the following important elements of the Ganoid structure, i, e. post and suborbital bones; postnareal cavities, branchiostegal, and arched branchihyal bones. On the other hand it has a large preorbital, bounding the frontal and maxillary to the flares, and the inner border of the orbit, as in Stegocephalous Batrachia; also a postorbital element, contributing to the formation of an extended supratemporal roof. Contrary to what has been found the case in most genera of Stegocephali, the maxillary appears to extend posteriorly to a free termination, as in modern Salamanders, and the supratemporalfobone presents a very prominent, obtuse, arched margin. This margin extends from the orbits on each side, and is inclined towards the posterior part of the cranium. There is therefore no quadratojugal piece. The maxillary and mandibular pieces are slender, flat bones, as in Menopoma; the form of the posterior or articular portion of the latter cannot be ascertained from the specimen. The more or less exposed part of the median region of the latter, exhibits a succession of shallow transverse notches, enclosing thirteen obtuse elevations. The former resemble rudimental lateral alp eolae for minute pleurodont teeth. A few other similar minute ribs, and, perhaps, a minute curved cone without sculpture, are the only other indications of dentition. The bones of the upper surface of the cranium are more readily interpreted by reference to those of Menopoma. A pail of narrow nasals, acuminate behind, penetrate between the frontals as far posteriorly as the posterior margins of the orbits. The suture between these is very distinct, and entirely straight. The preorbitals extend to above the orbit, and then appear to cease with a transverse suture. Between these and the nasals a broad triangular element enters on each side, not attaining the probable position of the nostrils. Each is divided by a longitudinal groove, which is probably a suture, and which would then divide the frontals from the parietals. The frontal would then divide the parietals entirely, as they do in Menopoma, for the anterior half of their length.' This would give the frontals a narrow form, acuminate in front, and bounded behind by a regular coarse, zig-zag transverse suture. The cranium behind this point is rugose, and the surface not well preserved, and it can only be said, that two peculiar grooves converge to a point between the posterior extremities of the frontons, like the boundaries of the supraoccipitals. The posterior boundary of the cranium with the condyles cannot be