96 OVR CARCINOLOGICAL FRIENDS. 



the beach-flea. Examine the legs of one of these 

 animals, and you will observe that they are disposed 

 on either side in two dissimilar series ; hence the 

 name of Amphipoda, double-footed, that has been 

 applied to the broad group to which the hopper 

 belongs. Two closely related, but larger, species, 

 of a gray rather than of an olive or brown color, 

 constitute the genius Talorchestia. 



A form much like the preceding, but with aquatic 

 habits, is found in both salt and fresh waters, 

 largely frequenting the meshes of the rock-weed 

 (Fucus). The Gammarus (PI. 7, Fig. 5), for so the 

 animal is known to naturalists, is a helpless creature 

 out of water, shuffling along on its side in a vain 

 endeavor to elude its pursuers or to regain the 

 water. It occurs in vast numbers in favored lo- 

 calities, contributing largely to the food-supply of 

 many of our coast fishes. 



Another interesting amphipod of our coast is 

 found abundantly on the surfaces of submarine 

 plants, and also on sponges, where it may be seen 

 moving about in the manner of the ordinary meas- 

 uring-worms, arching over its body, and advancing 

 alternately the two extremities. From this close 

 resemblance to the progression of the geometer 

 worms it has received the name of Gaprella geo- 

 metrica (PI. 7, Fig. 3). 



Of the less attractive group of the sow-bugs, 

 many of whose members, such as the Bopyrus, 

 already mentioned, are parasitic on the tissues of 

 other animals, but few forms are likely to come 

 to the notice of the visitor to the sands. One of 



