ADDENDUM. 159 



Addendum to Dr. Dawson' 's article on Air-Breathers of the 

 Coal Period. 



Through the kindness of the Council of the Geological Society 

 of London, the fine skeleton of Dendrerpeton Acadianum, sent by 

 me to the Society in 1861, has been returned for my inspection 

 in the preparation of this article. 



I am now able to state, in addition to the facts already publish- 

 ed, that the large furrowed teeth of the inner series were not 

 placed in the palatal bones, but on the maxillaries and intermax- 

 illaries, the outer series of smaller and simple teeth being borne 

 on the outer margin of these bones. The arrangement was thus 

 somewhat similar to that in Lepidosteus. Immediately within 

 the large teeth were the vomerine series, which were very numer- 

 ous and irregularly placed, but small, with the exception of a few 

 in front. They extended backward in two lines along both sides 

 of the palate, in this also resembling some ganoid fishes. 



In this specimen, the lower jaw, remaining in place under the 

 skull, is seen to contain, especially toward the front, long fur- 

 rowed teeth like those of the upper jaw, implanted in round soc- 

 kets on the broad upper surface of the mandible, with others more 

 simple and of smaller size. 



By carefully removing the stone, I have uncovered the occipital 

 condyles, which are double and square in outline, much like those 

 of Labyrinthodon, and not dissimilar from those of Sieboldia and 

 Menobranchus. 



Near the skull, the scales of the throat remain in their natural 

 position, and are seen to be densely imbricated, and arranged in 

 curved rows, diverging from the mesial line. The scales of the 

 abdomen are of larger size, and are scattered over the stone. 

 Those of the throat are of a narrow ovate form, those of the abdo- 

 men wider, and some of them tending to rhomboidal in outline. 



Twenty-four vertebrae, in all, are seen in the specimen. Of these 

 thirteen occur in continuous series, and appear to be lumbar. 

 They are of small size, relatively to the dimensions of the head 

 and limbs, and indicate a weak and flexible back. Other verte- 

 bras, not in regular series, are dorsal, and have strong transverse 

 processes with oblique articulating surfaces. A few are perhaps 

 cervical and caudal. The bodies of the vertebrae have continuous 

 bony walls, but thinner than in specimens of larger size. 



One half of the pelvis is well preserved, and shows a broad 



