LIFE OF THE PERIOD. 169 



through the shales and limestones ; and shell-fish of every 

 known order bivalve and univalve, deep-sea and shore 

 dweller occur throughout the entire system, though most 

 abundantly, of course, in the marine beds of the mountain 

 limestone. Fishes of many forms are likewise abundant, 

 especially in the lower series of the system, their shining 

 enamelled scales, predaceous teeth, and defensive fin-spines 

 being scattered through the shales, ironstones, and lime- 

 stones. Many were large and shark-like, their palatal teeth, 

 jaws, scales, and fin-spines indicating lengths from twelve 

 to eighteen and twenty feet, and bulky in proportion. Being 

 chiefly cartilaginous, their bodies have in most instances 

 utterly disappeared, and only their teeth or enamelled fin- 

 spines remain to testify to their existence. We have seen 

 hundreds of teeth and spines from a single layer of black- 

 band ironstone, and yet no other vestige of the fishes to 

 which they belonged, not even a patch of scales in juxta- 

 position, to indicate their affinities. Higher than fishes, 

 reptiles also make their decided appearance, most of them 

 aquatic and fish-like in form, though a few ascend to true 

 lacertilian or terrestrial species. Of the terrestrial fauna of 

 the period we know little ; but the insects, land-snails, and 

 reptiles of arboreal habits, which have been found in cer- 

 tain coal-fields, were surely not the sole inhabitants of the 

 carboniferous islands and continents, and we may safely 

 look forward to the discovery of other and higher forms of 

 which these were the necessary congeners. Even while we 

 write, the announcement of several new genera of reptiles 

 from the coal-field of Kilkenny gives additional encourage- 

 ment to this expectation, and all that seems necessary to 

 its fulfilment is merely more minute research and more 

 careful examination on the part of paleontologists. Indeed, 

 when we consider the difficulty of preserving terrestrial 

 organisms, how much they are subjected to waste and de- 



