SEA-SCORPIONS. 29 



forwards. We can fancy this creature propelling itself much in 

 the same way as a " water-beetle " rows itself through the water 

 in a pond. In all other crustaceans the antennae are used for 

 feeling about, but in the Pterygotus they are used as claws for 

 seizing the prey. 



In general external appearance, this huge Pterygotus greatly 

 reminds us of a tiny fresh-water crustacean, known as Cyclops- 

 because it has only one eye, like the giant in Homer's Odyssey. 

 This little creature, which is only T V inch in length, is an 

 inhabitant of ponds. From its large eyes, powerful oar-like 

 limbs, or appendages, and from the general form of its body, Dr. 

 Henry Woodward (the author of a learned monograph on these 

 creatures) concludes that the Pterygotus was a very active 

 animal; and the reader will easily gather from its pair of 

 antennae, converted at their extremities into nippers, and from 

 the nature of its " jaw-feet," that the creature was a hungry and 

 predaceous monster, seizing everything eatable that came in its 

 way. The whole family to which it belongs including Pterygotus, 

 Eurypterus, Slimonia, Stylonurus, and others seems to have been 

 fitted for rather rapid motion, if we may judge from the long 

 tapering and well-articulated body. In two forms (Pterygotus and 

 Slimonia) the tail-flap probably served both as a powerful pro- 

 peller, and as a rudder for directing the creature's course ; but 

 others, such as Eurypterus and Stylonurus, had long sword-like 

 tails, which may have assisted them to burrow into the sand, in 

 the same way that king-crabs do. Eurypterus remipes is shown 

 in Fig. 2. 



It has been stated above that our sea-scorpions are related to 

 the king-crabs. Now, this creature, it is well known, burrows into 

 the mud and sand at the bottom of the sea. This it does by 

 shoving its broad sharp-edged head-shield downwards, working 

 rapidly at the same time with its hinder feet, or appendages, and 

 by pushing with the long spike that forms a kind of tail. It will 

 thus sink deeper and deeper until nothing can be seen of its 



