CHAPTER XI 



THE HORSESHOE CRAB AND OTHER DENIZENS 

 OF SAND AND MUD 



" Neither fish, nor flesh, nor good red herring." 



— Dryden. 



THE horseshoe or king crab is an inter- 

 esting beast, the sole survivor of an 

 ancient and high-born lineage. An- 

 cient in that it is related to the trilobites, high 

 born because it suggests an alliance with the 

 curious ostracoderms. The first of these, the 

 trilobites, are found in the rocks of the Cam- 

 brian period, the most ancient of all fossil- 

 bearing rocks, and they became an important 

 race in the lower Silurian age, only to dwindle 

 and die out before the Palaeozoic times ended. 

 Incidentally we may learn a lesson from their 

 fall as well as from the fall of other groups 

 of animals now extinct, for they all, like the 

 ancient Romans, indulged in bizarre and ex- 

 travagant developments just before their de- 

 cadence. The ostracoderms form a strange 



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