30 EXTINCT MONSTERS. 



body, and only the eyes peep out of the mud. It will crawl and 

 wander about by night, but remains hidden by day. Some of 

 them are of large size, and occasionally measure two feet in 

 length. They possess six pairs of well-formed feet, the joints of 

 which, near the body, are armed with teeth and spines, and serve 



FlG. 2. Silurian merostomata. 

 I. Stylonurus. 2. Eurypterus. (After Woodward.) 



the purpose of jaws, being used to masticate the food and force 

 it into the mouth, which is situated between them. 



Now, this fact is of great importance; for it helps us to 

 understand the use of the four pairs of " jaw-feet " in our Sea- 



