172 THE OCEAN. 



endowed with the faculty of swimmino;. In the 

 common Crab all the feet, except the claws, ter- 

 minate in a sharp point, but in the present genus 

 the hindmost pair have the last joint flattened out 

 into a thin Ijut broad oval plate, the edge of which 

 is thickly fringed with fine hairs. This structure is 

 exactly parallel to that by which the foot of a perch- 

 ing bird is modified into the foot of a swimming 

 bird, the surface being dilated into a broad web ; or 

 to the wide fringe by which the hind feet of a water- 

 beetle are made such powerful oars ; the flattened 

 joint in the present case becoming a paddle, by the 

 stroke of which a rapid motion is obtained through 

 the water. These Swimming Crabs are very vora- 

 cious, preying upon the little shrimps that are nume- 

 rous about the weed, which they pursue and seize 

 with their pincers. Sometimes the Crab remains at 

 rest, but vigilant, until a shrimjD swims within reach, 

 when he grasps it with great quickness, and proceeds 

 to devour it by degrees. In doing this, he holds it 

 fast by one claw, while with the other he picks off 

 very daintily the legs and other members of his 

 prey, putting them bit by bit into his mouth, until 

 nothing remains but the tail, which he rejects. 



The weed is usually the resort of several small 

 species of fish, which doubtless congregate about 

 it for the sake of the minute Crustacea that are so 

 abundant. Among them I have found a very in- 

 teresting little species of Toad-fish {Antennarius), 

 whose pectoral and ventral fins project so far from 

 the surface of the body as to expose the joint, and 

 thus take th*^ form of the feet of the quadruped. It 



