ix.] PALAEONTOLOGY AND EVOLUTION. 185 



sauria, more specialized than any which now exist, 

 abounded. 



There is one division of the Amphibia which offers 

 especially important evidence upon this point, inasmuch 

 as it bridges over the gap between the Mesozoic and the" 

 Palaeozoic formations (often supposed to be of such pro- 

 digious magnitude), extending, as it does, from the bottom 

 of the Carboniferous series to the top of the Trias, if not 

 into the Lias. I refer to the Labyrinth odonts. As the 

 address of 1862 was passing through the press, I was 

 able to mention, in a note, the discovery of a large 

 Labyrinthodont, with well-ossified vertebrae, in the Edin- 

 burgh coal-field. Since that time eight or ten distinct 

 genera of Labyrinthodonts have been discovered in the 

 Carboniferous rocks of England, Scotland, and Ireland, 

 not to mention the American forms described by Principal 

 Dawson and Professor Cope. So that, at the present 

 time, the Labyrinthodont Fauna of the Carboniferous 

 rocks is more extensive and diversified than that of the 

 Trias, while its chief types, so far as osteology enables us 

 to judge, are quite as highly organized. Thus it is certain 

 that a comparatively highly organized vertebrate type, 

 such as that of the Labyrinthodonts, is capable of per- 

 sisting, with no considerable change, through the period 

 represented by the vast deposits which constitute the 

 Carboniferous, the Permian, and the Triassic formations. 



The very remarkable results which have been brought 

 to light by the sounding and dredging operations, which 

 have been carried on with such remarkable success by 

 the expeditions sent out by our own, the American, and 

 the Swedish Governments, under the supervision of able 

 naturalists, have a bearing in the same direction. These 

 investigations have demonstrated the existence, at great 

 depths in the ocean, of living animals in some cases 

 identical with, in others very similar to, those which are 



