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MARINE INVERTEBRATES 



habit ponds and streams of fresh water, and still others are found 

 along the shores of all oceans, abounding among the marine vege- 

 tation of the shallow waters. Some swim free in the open sea; 

 others are brought up from the* greatest depths. Others, again, 

 are parasites, and live in the internal organs of fishes and prawns. 

 Sometimes a prawn is found having what appears like a very 

 swollen throat, which actually is a little parasitic isopod of the 

 family Bopyridw attached to its gills. 



GENUS Cirolana 



C. concharum. The body consists of fourteen segments, the first 

 being the head, the next seven the thorax, and the last six the abdomen. 

 On the head are the triangular eyes, the antennules, and 

 the antennae, and underneath is the mouth, which is 

 covered by the maxillipeds. The dorsal sui'face is more 

 or less rounded. At the bases of all the segmental thoracic 

 rings excepting the first one are sutures marking off square, 

 scale-like pieces (epimerd). The epimera form a border 

 to the side margins. The legs are attached to the epimera, 

 which are, in fact, the upper segments of the legs. The 

 first three pairs of legs have a general resemblance to one 

 another, and are directed forward. The last four pairs are 

 much longer and flatter, and are directed backward. The 

 telson, or last segment, is triangular, and the square or 

 blunt apex is fringed with hairs. On the ventral surface 

 of the thorax in the adult females there is a long pouch 

 for the reception and development of the eggs. This spe- 

 cies is usually about one and a half inches in length, but sometimes is 

 longer. Its color is yellowish, with a brown edge on the posterior margins 

 of the segments, somewhat translucent in the thinner parts. It is found 

 from Cape Cod to South Carolina, swimming about in 

 shallow water, and is especially abundant in winter. 



GENUS Limnoria 



L. lignorum, the gribble. This little isopod is very 

 destructive in its habits, boring into submerged wood- 

 work, like the ship-worm (Teredo), and doing great 

 damage to the piles of wharves, etc. It burrows to the 

 depth of half an inch, and completely honeycombs the 

 surface of the wood, which then scales off or rapidly 

 decays, and is washed away by the waves. The animal 

 then begins anew, and in a short time, or at the rate of 

 about an inch a year, piles diminish in diameter where 

 Limnoria is plentiful, and are finally destroyed unless protected from 

 these little crustaceans by a sheathing of metal. Although considered 

 as pests, they have an economic value not so often recognized, as they 

 attack all driftwood, and in time entirely destroy floating and water- 



lAmnoria liynorum, 

 the gribble. 



