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OF MULTIVALVE SHELL-FISH. 



OF thefe are principally two kinds ; fuch as move, and fuch as arc 

 ftationary : the firft are often known by the name of/ea-eggs ; by 

 naturalifts. Echini, or Urchins : the latter are called Pholadcs cr File- 

 Fifli. Of both there are feveral forts. 



The Sea-Urchin may be compared to the huflc of a cheftnut, being 

 round, and with bony prickles on every fide. The mouth is below, 

 the vent above ; the Ihell is a hollow vafe, refembling a fcooped apple, 

 filled with a foft, mufcular fubftance, through which the inteftines wind 

 from the bottom to the top. The mouth is large and red, furnilhed 

 with five Iharp teeth, which are eafily difcerned. The jaws are flrength- 

 cned by five fmall bones, in the centre of which is a fmall fleihy tongue; 

 from this the inteftines make a winding of five Ipires, round the in- 

 ternal fides of the ihell, ending at the vent at top. Its horns are move- . 

 able, like the horns of a fnail, and point from every part of the body, 

 ferving at once as legs to move on, as arms to feel with, and as inftru- 

 ments of capture and defence. Between thefe horns it has fpines not en- 

 dued with fuch a fhare of motion. The fpines are hard and prickly ; 

 the horns fofc, longer than the fpines, and hid at the bafes of the fpines. 

 This apparatus is only feen*when the animal is hunting its prey at the 

 bottom of the water ; for, a few minutes after it is taken, all the horns are 

 withdrawn into the body, and moft of the fpines drop off. FurniQied 

 with two thoufand fpines, and twelve hundred horns, all ferving for legs, 

 and from their number feeming to impede each other's motion, yet it 

 runs not without fwiftnefs at the bottom, and it is fometimes not eafy to 

 overtake it. It is often taken on the ebb, by following it in fliallow wa- 

 ter, either in an ozier baflcer, or fimply with the hand. Both the fpines 

 and the horns affift its motion j and the animal is ufually feen running 

 with the mouth downward. 



Some kinds are as good eating as the lobfterj their eggs, which are 

 of a deep red, are confidered as a very great delicacy. Of others the 

 tafte is but indifferent ; and in all places,except the Mediterranean, they 

 are little fought for, except as objedts of curiofity. 



The Acorn Shell-fifli, the Thumb-footed Shell-fifii, and the Barnacle, 

 are fixed to one fpot, and appear to vegetate from a ftalk like a kind of 

 fungus, growing in the deep, deftitute of animal life as well as motion : 



Part V. No. 30. X x but 



