AND AYES OF NORTH AMERICA. 13 



posteriorly as the anterior margin of the orbits. The external nostrils are large and opposite the inner margin of 

 the orbit on each side. This separation of the nares is associated with a greater transverse extent of the x'remaxil- 

 laries than in some of the genera. These have been set with numerous teeth, judging by their small impressions ; 

 no larger ones have left traces, and no traces of any on the maxillaries. The teeth of the genera before described 

 are all much larger relatively, indicating still further the diversity between them. 



A fragment of mandible remains, but without teeth or external surface. It shows a large internal canal. 



Measurements. Lines. 



Total length cranium, 25.5 



Width do. three lines behind orbits, 24 

 Do. between orbits, 7.5 



Do. do. nares, 5 



Do. occipital condyles, 2.2 



Do. of supraoccipital bones, 6 



Do. of right parietal, C 



Extent of premaxillaries, 8.7 



Length orbit, 6 



From the Coal Measures at Linton, Columbiana county, Ohio. Discovered by Dr. 

 Jno. S. Newberry. When the remainder of the skeleton of this species is known, its 

 generic relations will be better established. 



Another cranium accompanies the collection, which belongs to a species distinct from 

 the last. The muzzle is not so broadly rounded and the premaxillary teeth are relative- 

 ly much larger. The sculpture is more delicate with the ridges more acute. The orbits 

 and nares are not defined. The maxillary is well preserved for a length of an inch ; its 

 teeth are smaller than the premaxilliries ; I count four in a line ; crown simple conic. 

 External surface of maxillary not very strongly sculptured. 



This species cannot be referred to its genus without further material. I therefore do 

 not name it. 



DENDRERPETON ACADIANUM, Owen. 



Quart. Joum. Geol. Soc. X., 1853, 81. Dawson, Loc. Cit. 

 Coal Measures. Joggins, of Nova Scotia." 



DENDRERPETON OWENII, Dawson. 



Canadian Naturalist and Geologist, VIII., 161. 

 Coal Measures : as the last. 



HYLERPETON, Owen- 



HYLERPETON DAWSONI, Owen. 



Joum. Geol. Loc. Lond. Loc. Cit. Dawson, Canadian Naturalist and Geologist, VIII., 272. 

 Carboniferous Coal Measures. The Joggins, Nova Scotia. 

 AMERf. PHILOSO. SOC VOL. XIV. 4 



