AVD AVES OF NORTH AMERICA. 11 



readily determined. "When the postorbital roof bone is raised up, the meeting of two 

 gular dermal bones, as I interpret them, is seen. One of these is a plate directed 

 backwards and outwards, bearing minute radiating lines on its upper surface. It meets a 

 similar flat plate directed forwards and outwards with similar lines radiating to the 

 circumference. The inner margins of these plates were not seen. 



The orbits are remarkably small, and situated probably near the middle of the 

 longitudinal measurement of the cranium. The external nares are not defined, but 

 symmetrical depressions in the position they usually occupy in Salamanders are distinct. 



The general form recalls Menopoma, particularly the small orbits. A slender curved 

 bone with a slightly dilated and truncate extremity, lying by the cranium in connection 

 with the mandible, is like a branchihyal of that genus. Nevertheless it cannot be 

 positively assigned to that genus, as numerous cycloid scales of fishes are on the same 

 block. 



PARIOSTEGTTS MYOPS, Cope. 



The surfaces of the cranial bones are little sculptured ; there are small tuberculiform elevations on the parietal 

 and more numerous oues on the preorbitals. The postorbitals show the strongest markings of elongated pits, which 

 radiate to their circumference, leaving a smooth obtuse border. The nasals present a series of small warts at a little 

 distance on each side of their common suture, and transverse to it. The surface of the maxillary is marked with 

 longitudinal grooves and shallow pits. 



Kb suture separating niaxillaries and premaxillaries can be traced with certainty, though the bones of the jaw 

 are interrupted at the usual place of suture, opposite the nostril. 



Measurements. _ Lines. 



Length of specimen (including mandible), 18 



Width between outer convexities postorbitals, 17 



Do. do. inner borders orbit, 11 



Do. of same without preorbitals, 8 



Do. of nasals at middle, 2.5 



Do. of orbit, 1.5 



Length of frontal and nasal premaxillary, 11 



Do. of supposed branchihyal, 12 



The name is derived from the roof-like postorbitals with free lateral margin. 



Locality. — Coal bed of the Keuper Triassic, Chatham county, North Carolina. The 

 species was discovered by Prof. Jos. Leidy, who handed it to me for description. It is in 

 the Museum of the Academy Nat. Sciences of this city. 



