280 THE OLDEST AIR-BREATHERS 



when they remain together, are so much crushed as to render 

 the shape of the skull not easily discernible. They are smooth 

 on the outer surface to the naked eye ; and under a lens show 

 only delicate, uneven striae and minute dots. They are more 

 dense and hard than those of Dendrerpeton, and the bone cells 

 are more elongated in form. The bones of the snout would 

 seem to have been somewhat elongated and narrow. A speci- 

 men in my possession shows the parietal and occipital bones, 

 or the greater part of them, united and retaining their form. 

 We learn from them that the brain case was rounded, and that 

 there was a parietal foramen. There would seem also to have 

 been two occipital condyles, as in modern Batrachians. Several 

 well-preserved specimens of the maxillary and mandibular 

 bones have been obtained. They are smooth, or nearly so, 

 like those of the skull, and are furnished with numerous sharp, 

 conical teeth, anchylosed to the jaw, in a partial groove 

 formed by the outer ridge of the bone. In the anterior part of 

 the lower jaw there is a group of teeth larger than the others. 

 The total number of teeth in each ramus of the lower jaw was 

 about forty, and the number in each maxillary bone about 

 thirty. The teeth are perfectly simple, hollow within, and 

 with very fine radiating tubes of ivory. The vertebras have 

 the bodies cyclindrical or hour-glass shaped, covered with a 

 thin, hard, bony plate, and having within a cavity of the form 

 of two cones, attached by the apices. This cavity was com- 

 pletely surrounded by bone, as it is filled with stained calcspar 

 in the same manner as the cavities of the limb bones. It was 

 probably occupied by cartilage. The vertebrae were apparently 

 bi-concave, and are furnished with upper and lateral processes 

 similar to those of small lacertian animals. The ribs are long, 

 curved, and at the proximal end have a shoulder and neck. 

 They are hollow, with thin hard bony walls. The anterior 

 limb, judging from the fragment procured, seems to have been 

 slender, with long toes, four or ssibly five in number. The 



