54 EXTINCT MONSTERS 
well-preserved specimens. There are five pairs of appendages, 
all attached under or near the head. Behind the head follow 
twelve rings, or segments, the last of which forms the tail, two 
at least of these bore gills for breathing. All but two of them, 
below the mouth, must have been beautifully articulated, so as 
to allow them to move freely, as we see in the lobster of the 
present day. But look at that lowest and largest pair of append- 
ages, the end joints of which are flattened out, and you will see 
that they must have been a powerful oar-like apparatus for 
Swimming 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 
antenne are used for feeling about, but in the Pterygotus they 
are used as claws for seizing the prey. 
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) con- 
cludes that the Pterygotus was a very active animal; and the 
reader will easily gather from its pair of antenne, 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, 
Shmonia, 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 propeller, 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. 7, A 
