44:4 



AMTHBOPODA. 



Order I. Xiphosura. 

 Cephalothorax large ; abdomen terminated by a long spiniform telson. 

 Limulus x>olrjpliemiis of our east coast, commonly known as king crab 



Fig. 457. Fig. 45S. 



Fig. 457. — Limulus polyphevius^* horseshoe crab (orig.). 



Fig. 458.— Ventral surface of Lhnidus mnluccanus. (From Ludwig-Leunis.} 1. 

 chelicerae ; 2-5, walking feet : 6' pushing foot; a", flabelluni ; 7, genital operculum; 

 8, gills (there should be five) ; 9, base of telson. 



or horseshoe crab. Other species on eastern shore of eastern continent. 

 They burrow beneath the sand and mud of the bottom and feed on worms. 

 In the spring they come to the sliore to lay eggs. 



Order II. Eurypterida. 



Extinct Silurian and Devonian forms with small cephalothorax and 

 large twelve-jointed abdomen. The animals are intermediate between the 

 xiphosures and the scorpions. Enrypterus ; Pterygotus. some species 

 seven feet long. 



Suh Class II. Araclinida. 



Under this name are included a number of orders of greater or 

 less extent which can be arranged around the spiders, or Aranea. 

 as a centre. There is considerable modification of form, and the 

 following account applies only to the more tyijical groirps. In 

 these the cejihalothorax and abdomen are separated by a di.stinct 

 line, and since the abdominal appendages almost entirely disappear 

 in the adult, the number of somites can only be ascertained where 

 tlieir boundaries are evident. 'J'he number varies between six in 

 the phah^ngids and thirteen in the scorpions. 



The cephalothorax is, except in the iSolpirgidaj, a single piece 



