AMPHIPODS 289 



are distinctly marked, and it terminates in long, forked spines, which 

 are longer than the telson. It is found from New Jersey northward. 



ORDER ARTHROSTRACA 

 SUBORDER AMPHIPODA 



The Amphipoda have a laterally compressed body,with gills on the 

 thoracic feet and an elongated abdomen. The segments of the 

 thorax are not united, nor covered by a carapace, but the whole 

 body is covered with a segmented, polished, flexible cuticle. The 

 three anterior legs of the abdomen are for swimming-feet, and 

 the posterior ones are adapted for springing. The antennae are 

 long and hairy. The amphipods comprise the beach-fleas and 

 many other small crustaceans which abound between tide-marks 

 on all beaches. Besides serving in no small measure as food for 

 fishes, they are scavengers of the beach, and consume large quan- 

 tities of waste matter. They are sometimes used in preparing 

 skeletons for anatomical specimens. Animals to be skeletonized, 

 being fastened to boards and anchored just below the surface of 

 the water in sheltered places, are divested of all flesh in a few 

 hours, and the bones are more completely cleaned than if pre- 

 pared by a naturalist. 



GENUS Orchestia 



O. agilis, the beach-flea. These little crustaceans exist in countless 

 numbers under the masses of sea- wrack on the beach. When disturbed they 

 jump about with great agility by means of the last 

 three pairs of abdominal feet, which are adapted 

 to this purpose. In color the animal is brown 

 and much resembles the decaying seaweeds 

 among which it lives and upon which it probably 

 feeds. The antennuies are short, the antennae 

 long, on two long, jointed bases. The second 



pair of feet in the males terminate in chelae. The last abdominal appen- 

 dages are stiff and pointed backward. The abdomen is curved under. 

 The length of Orchestia is half an inch or less. Some species occur on all 

 beaches. 0. agilis ranges from New Jersey to Greenland. 



GENUS Talorchestia 



T. longicomis (Talitrus longicomis). This species is similar to 

 Orchestia agilis, but is about an inch long when mature and of a paler 



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