SECTION XIII 

 The Trilobites 



In this appeal to the ancient Crustacean forms to 

 ascertain whether they lend any support to our theory 

 of the origin of the class, we began with Limulus, not 

 because it is more nearly related either to Apus or to 

 our bent Annelid than are the Trilobites, but because 

 its anatomy is so well known that it admitted of closer 

 comparison, and further because its relation to the 

 Trilobites is fairly well established. It thus formed 

 a sort of link for the purposes of our comparison, to 

 connect the Apodidse with the Trilobites and the 

 Eurypterida^. That Limulus and the Trilobites are 

 closely related is now generally acknowledged. 



Having shown that Limulus is, like Apus, derivable 

 from a bent Annelid, if we can only show that the 

 organisation of the Trilobites is also best explained 

 by attributing to it a similar origin, we shall be able 

 to group the Xiphosurida^, the Trilobites, and the 

 Apodidai for the first time in a natural system. 



It is important to bear in mind that the Trilobites 



P 



