218 AMPHIPODA. 



the name of Opossum Shrimps from the curious 

 pouch, formed of plates attached to the abdominal 

 legs, in which the female protects both her eggs 

 and young until the latter have attained consider- 

 able development. 



The Opossum Shrimps abound in the northern 



seas. The Arctic Ocean 

 teems with myriads, 

 forming, not troops, but- 

 vast clouds, spreading 

 over square leagues of 

 water, and affording suffi- 

 cient and most nutritive 

 food for the whale, and 

 for the prodigious shoals 

 of salmon that visit the 



FIG. lee.-oiossuM SHKIMI-. shores of Boothia during 



July and August, and 



upon which the inhabitants of that dreary region 

 depend in a great measure for their supply of winter 

 provisions. During summer the Opossum Shrimps 

 absolutely crowd the mouths of the rivers, and there 

 their destroyers revel in a continual feast. 



THIRD ORDER OF CRUSTACEANS. 

 AMPHIPODA.* 



In the succeeding Crustaceans the eyes are sessile, 

 that is, not supported on jointed stems, and conse- 

 quently motionless. The legs appended to the diffe- 

 rent segments vary much in their structure. The 

 Amphipods have their limbs arranged in two groups 

 opposed to each other. Their body is generally 

 compressed and curved towards the breast ; they 

 swim and leap with facility, but always lying on one 

 side. Some of them inhabit fresh water, but by far 

 the greater number are marine. 



* afLtyi, ampin, of two sorts ; TTOVS, pous, a foot. 



