364 



ZGOLOGy. 



[SfctXL 



low water, many bivalves, such as 5c>/eri.9, Cardia^ Te1lin(B, 

 &c., will be procured alive ; andj if the inhabitants of the 

 coast be accustomed to diving, their services should be 

 secured for deeper water. Care must be taken not to 

 separate the ligament which binds the hinge. When the 

 animal is dead the shell will gape, and the soft parts 

 may then be removed without injury. Attempts to open 

 bivalves, while the animals are alive, generally terminate 

 in great injury to the shells. 



the dredge is indispensable. 



For deep-sea shell 

 Dredging requires experience to judge of the length of 

 rope to be used ; if there be too much on a sandy bottom, 

 the dredge will bury itself; if too little, it will not scrape 

 properly : on rocky boitonis the rope must be kept as short 

 as possible ; in deep water the dredge can only be made 



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to act effectually by placing a weight on the line, which. 

 as a rule, may be about one-third of the weight of the 

 dredge, and placed on the line at about two-thirds of the 

 depth of the water ; the object is to sink the rope, and 

 covmteract the tendency it has to float the dredge. The 

 contents 



01 



the dredge are best examined by means 

 of sieves, of which three should be used, one over the 

 other, first a riddle, next a wheat sieve, and third an oat 

 sieve ; these may be fastened together, the contents of 

 the dredge being emptied into the riddle, and water being 

 poured upon them, the mud, &c. will be washed off, and 

 the contents separated, so as to be very easily examined ; 

 by this plan 



a 



I 



hundred fold more will be discovered^ than 

 can be found by searching in mud or sand in the usual 

 manner. Besides shells, numbers of crabs, star-fishes, 

 sea urchins^ worms, corals, zoophytes, alga?, &c. are 

 procured by the dredge. 



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