84 THE OPEN BOOK OF NATURE 
Devonian times, and has been christened Dipierus. 
Its fossil remains have been found in Old Red 
Sandstone rocks of Scotland and Russia. Ceratodus 
means “‘ horn-tooth ” ; Dipterus is from the Greek 
dipteros =two-winged. Fossils of the true Ceratodus 
have been discovered in Triassic rocks. Dipterus 
differed from Ceratodus in having a triangular tail 
and bony scales. 
If you can get to a museum you must inquire for 
the fossil fishes, and examine them carefully ; you 
will find them most interesting. A look over the 
collection in the London Natural History Museum 
will be a revelation to you. 
2. Amphibians (Greek, amphi=both, bios = life). 
—Cold-blooded animals capable of living both in 
water and on land. In water they breathe by gills, 
and on land or in air by lungs. Toads, newts, and 
frogs will be familiar examples. Fossil Amphibians 
first appear in Carboniferous strata, and in that 
Period the Amphibia seem to have been the most 
highly developed living creatures. They then had 
no big reptiles, nor lions and tigers to compete with 
them for the mastery of the world. The order of 
Carboniferous Amphibians is long extinct. ‘They 
are called Labyrinthodonts—t.e., labyrinth-toothed— 
because cross-sections of the teeth of most of them — 
show mazelike patterns. The Labyrinthodonts 
must have been like modern newts and salamanders. 
Most of them could swim and walk; at least, the 
well-developed tails and legs which fossil remains 
exhibit seem to bear out such a conclusion. Some 
of them were wholly, and others partly, protected 
by a coat of mail made up of scales ; their chests 
