206 PALEONTOLOGY. 



structure of the teeth, the sculpturing of some broad cranial 

 plates, and the structure and proportions of certain limb-bones, 

 to the genus Archegosaurus* The subsequent discovery of 

 carinate scales with bones of the Dendrerpeton adds to the pro- 

 bability of its appertaining to the Ganocephalous order. A 

 second kind of reptile (Hylonomus), and perhaps a third, 

 together with a centipede (Xylohius), and shells of the air- 

 breathing-snail (Dendropitpa), have rewarded Dr. Dawson's 

 later explorations of the hollows of the old coal-forming trees 

 of the carboniferous deposits of Nova Scotia. Thus air- 

 breathing mollusks, articulates, and vertebrates, concur with 

 the rich terrestrial vegetation to testify to the life-sustaining 

 power of the atmosphere in the oldest division of the geological 

 periods of the history of the earth. 



Order II. — Labyrinthodontia. 



Head defended, as in the Ganocephala, by a continuous casque 

 of externally sculptured and unusually hard and 

 polished osseous plates, including the supplementary 

 "post-orbital" and "super-temporal" bones, but leaving 

 a " foramen parietale." Two occipital condyles. Vomer 

 divided and dentigerous. Two nostrils. Vertebral 

 bodies, as well as arches, ossified, biconcave. Pleur- 

 apophyses of the trunk, long and bent. Teeth rendered 

 complex by undulation and side branches of the con- 

 verging folds of cement, whence the name of the order. 



The reptiles presenting the above characters have been 

 divided into genera, according to minor modifications exem- 

 plified by the form and proportions of the skull, and by the 

 relative position and size of the orbital, nasal, and temporal 

 cavities. 



Genus Baphetes, Ow. 



* Quarterly Journal of the Geological Society, vol. ix., 1853. 



