AIR-BREATIIERS OF THE COAL RERIOD. 273 



the most interesting specimens contained in the last of these trees 

 which I had an opportunity to examine. It consisted of the de- 

 tached bones of a reptile scattered over a surface so blurred and 

 stained that they escaped my notice until most of them were lost; 

 and I waa able to secure only a jaw bone and fragments of the 

 skull, with a few of the other bones. On these fragments Prof. 

 Owen founded the genus Ilylerpeton and the species named at 

 the head of this article. His description is as follows : 



" This specimen consists of the left ramus of a lower jaw (Fig, 

 32), which has been dislocated from the crushed head, of which 

 the fore end of the left premaxillary is preserved, terminating 

 near the middle of the series of the teeth of the more advanced 

 mandible. A fragment of the left maxillary, which has been se- 

 parated from the premaxillary, overlaps the hinder mandibular 

 teeth. The fore part of the mandible is wanting. The teeth in 

 the remaining part are larger and fewer, in proportion to the jaw- 

 bone, than in Hylonomus or Dendrerpeton. They have thicker 

 and more obtusely terminated crowns ; they are close-set where 

 the series is complete at the fore part of the jaw, and their base 

 appears to have been anchylosed to shallow depressions on the 

 alveolar surface. The shape of what is preserved of the upper 

 jaw affords the only evidence, and not very decisively, that the 

 present fossil is not part of a fish. It inclines the balance, how- 

 ever, to the reptilian side ; and, accepting such indication of the 

 class-relations of the fossil, it must be referred to a genus of Rep- 

 tilia distinct from those it is associated with in the Nova Scotian 

 coal, and for which genus I would suggest the term Ilylerpeton. 



" A small part of the external surface of the dentary bone shows 

 a longitudinally wrinkled and striate or fibrous character. The 

 outer bony wall, broken away from the hinder half of the dentary, 

 shows a large cavity, now occupied by a fine greyish matrix,, 

 with a smooth surface, the bony wall. of which cavity has been 

 thin and compact. We have here the mark of incomplete ossifica- 

 tion, like that in the skeleton of Archegomurus. The crushed 

 fore part of the right dentary bone, with remains of a few teeth, 

 is below the left dentary, and exemplifies a similar structure,. 

 The teeth slightly diminish, though more in breadth than lengthy 

 towards the fore part of the series : here there are nine teeth in 

 an alveolar extent of 10 millimeters, or nearly 5 lines. The base 

 of the teeth is longitudinally fissured, but the fissures do not ex- 

 tend upon the exserted crown. In their general characters, the* 

 Can. Nat. 18 Vol. VIII. 



