2 24 Dzi'cllers of the Sea and Shore 



is that the systematic place of this ancient creature has 

 always been a debatable one, many naturalists holding 

 quite opposite opinions as to its position among animals. 

 It gets its name from the three prominent lobes, or 

 regions, into which the body is divided: cephalic, tho- 

 racic, and abdominal; that is, the regions of the head, 

 fore body, and hind body. Although more than five 

 hundred species are known, many of them diverging 

 widely in structure, they all agree in having a head 

 shield more or less crescentic in shape; and, except in 

 the case of a few blind forms, this head shield bears a 

 pair of large compound eyes. Succeeding the cephalic 

 region is a varying number of free segments, each of 

 which consists of an arched section flanked by a pair of 

 lateral plates. This, the mid-region of the body, is 

 terminated by the abdomen, similarly arched, but 

 having the segments fused. 



Fossils of the trilobite in which the appendages of 

 the under side can be distinctly traced, have been ex- 

 ceedingly rare, and only in one genus (Triarthnis) is 

 their structure accurately known. In this Instance it 

 was discovered that each segment of the body carries 

 a pair of legs jointed to the lateral plates. In the 

 region of the mouth the base of the legs was armed 

 with teeth, subserving the purpose of mastication, or 

 the reducing of its food. 



The trilobite, no doubt, lived along the seashore 

 where it slowly plowed Its way in the mud and sand 

 after worms and other soft-bodied animals. It prob- 

 ably became extinct long before flowering plants made 

 their appearance on the land; which is to say. It died 

 out about the time the coal beds were formed. The 



