THE DEVONIAN AGE. 93 



to liave been no unusual occurrence in the history of 

 life.* 



If the Devonian witnessed the culmination of the 

 Palaeozoic corals, its later stages saw the final de- 

 cadence of the great dynasty of the Trilobites. Of 

 these creatures there are in the Devonian some large 

 and ornate species, remarkable for their spines and 

 tubercles ; as if in this, the latter day of their do- 

 minion, they had fallen into habits of luxurious deco- 

 ration unknown to their sterner predecessors, and at 

 the same time had found it necessary to surround 

 their now disputed privileges with new safeguards of 

 defensive armour. Not improbably the decadence 

 of the Trilobites may have been connected with the 

 introduction of the numerous and formidable fishes of 

 the period. 



But while the venerable race of the Trilobites was 

 preparing to fight its last and unsuccessful battle, 

 another and scarcely less ancient tribe of crustaceans, 

 the Eurypterids, already strong in the Silurian, was 

 armed with new and formidable powers. The 

 Pterygotus anglicus, which should have been named 

 scoticus, since its head- quarters are in Scotland, was 

 in point of size the greatest of known crustaceans, 

 recent or fossil. According to Mr. Henry Woodward, 

 who has published an admirable description and 

 figures of the creature in the Palseontographical 



* Verril has suggested that the Tabulata may be divided 

 into two groups, one referable to Actinoids, the other ta 

 Ilydroids. 



