190 WHAT IS LIFE? 



and warm atmosphere grew to a great size. Our 

 modern horse-tails had their allies in huge trees among 

 the Carboniferous jungles, and the familiar club-moss 

 of our hills, now a low creeping plant, was represented 

 by tall stemmed trees that rose fifty feet or more into 

 the air. 



Amongst the forms of animal Hfe that existed, when 

 these layers of rocks were being formed, are corals and 

 crinoids, the latter were so abundant that their sepa- 

 rate joints formed solid masses of rock several hundred 

 feet in thickness. The ordinary bivalves the la-nielli - 

 branchs (mollusks of which the mussel is a type) 

 in these strata, begin to hold their own against the 

 brachiopods (a simpler form of bivalve), the latter 

 more freely existed in previous formations. Some of 

 the genera that now spring into life exist to this day. 

 Trilobites almost wholly disappear. Fishes existed in 

 variety. True terrestrial animals seem more abundant 

 during this period. Ancient forms of may-fly, cock- 

 roach, cricket, and large beetles are found in these 

 formations. Insects indeed flourished when these 

 layers were deposited, some of considerable size, the 

 spread of the wings measuring fourteen inches or more, 

 and one species had a wing twelve inches in length. 

 Scorpions of gigantic size have been found. Forms of 

 spiders appear. Large amphibious animals, capable of 

 living on land or in water, measuring seven or eight 

 feet long, lived then. They were of the Salamander 

 type, with relatively weak limbs and long tails some- 

 times the limbs were undeveloped, so that the body 

 was serpent-like. On the whole the types of life were 

 of a higher form than that which had gone before. 



The Carboniferous strata are found in the British 



