THE TRIL0B1 





Limttlus, and is often variously ornamented with tn 

 cles and spines. The ; - divided into three J' 



tudinal lobes, the central situated the 



heart a.s in Limulus. The body differs from that <»f the 



T~~~^x 





9 



i 





l'-'4 Young Hoi sesl i 'rab. 



Natural si/..- and enlargi 





nine Trilobite. 



horseshoe era! in being divided into a true head sting 



of six segments bearing jointed appendages, somewhat like 

 those of the Merostomata, with from two to twenty 

 tiuct thon spnents (probably bearing short jointed 



In. 136.— Restored secti f the thorax if ter Wal- 



cott. c. cai apace; i ,. endopodite; 

 podal or respirator] pari oi the appends 



limbs not extending beyond the edge of the body). The 

 abdomen consists of several (greatest number twenty-eight) 

 coalesced segments, forming a solid portion {pygidi 

 sometimes ending in a spine. The larval trilobite (F _ 125) 



