THE TRIGGER-FISH 



than they are today. They were predominant among 

 the fauna. 



The appearance of these vanished seas, of the 

 population which filled their waters and crawled over 

 their beds, the fades in a word, was very different 

 from that which came afterwards, down to our own 



Fig. 17. — Trilobite (Paradoxides 

 spinosus), a fossil found in Cam- 

 brian strata of the beginning of 

 the Palaeozoic era. 



Fig. 18.— The King-crab. The 

 body, not including the tail- 

 like appendage, may reach 

 a foot in length. 



time. The mass of the population, so far as fishes 

 were concerned, was made up of these armoured 

 species, covered by an outer skeleton, and having 

 only a small cartilaginous inner skeleton. In the 

 Palaeozoic era that population was characteristic of 

 the oceans. In those days the continents were probably 

 low, and of no great extent; animal life on land was 

 meagre and restricted ; life centred particularly in 

 the seas, and the armoured fishes were dominant 

 86 



