10 



THE EXTINCT BATRACHIA, REPTILIA 



PAEIOSTEGTJS, Cope. 

 Proceed. Acad. Nat. Sci. 1868, 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 some of its characters arc somewhat ichthyie, it 

 lacks the following important elements of the Ganoid structure, i, e. post and suborbital 

 bones; postnareal cavities, branchiostegal, and arched branchihyal hones. On the other 

 hand it has a large preorbital, bounding the frontal and maxillary to the naxes, and the 

 inner border of the orbit, as in Stegocephalous Batrachia; also a postorbital (-lenient. 

 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 supratemporal bone 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 hones, as in Menopoma; the 

 form of the posterior or articular portion of the hitter cannot he; 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 alveolae for minute pleurodont teeth. A few other 

 similar minute ribs, and, perhaps, a, minute curved (-one without sculpture, are the only 

 other indications of dentition. 



'Hie bones of the upper surface of the cranium are more readily interpreted by 

 reference to those of Menopoma. A pair of narrow nasals, acuminate behind, penetrate 

 between the frontals as Ik. i- 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 (he frontals from the parietals. 'Hie frontal would then divide 

 theparietals 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 he said, that two peculiar grooves converge 

 to a point between the posterior extremities of the frontals, like the boundaries of the 

 supraoccipitals. The posterior boundary of the cranium with the condyles cannot be 



