130 CRUSTACEA AND MOLLU6CA FOR 



effected has not been explained. I have never been able to 

 keep the Drill alive any length of time in confinement. 



The Crepidula — of which there are four species (C. for- 

 nicator— Plate IX., Fig. 5), although very common with 

 us, I have not been able to keep in an Aquarium. These 

 crepidulee are found adhering to each other aud to different 

 shells and stones ; aud when adhering to a Fcclen, the mar- 

 gin is observed to have undulations corresponding to the ribs 

 of the latter. I have seen four or five adhering to each 

 other. This is the little boat-shaped shell that we pick up 

 on the margin of Long Island Sound. It makes a capital 

 bottom for our tank, when mixed with Anemia and stones. 

 Many other univalve marine shells may be introduced ; 

 but I have tried very few as yet, being satisfied, generally, 

 with the Bv.ccinum obsoldum, which is easy to procure and 

 a pretty good scavenger. Of the bivalves, none are safe 

 in our Aquarium, for, when they die, it is generally with 

 closed shells, and we do not find out their demise until the 

 water is fouled by their decomposition and it is too late. 

 Oysters (Ostrea) can be kept, for a short time, for curi- 

 osity, and when they are cut up they make good food for 

 the crabs. The creature in the little gold-shell so common 

 on the coast (Anemia cphippinm), will not live more than 

 two weeks, but whilst it does, it is an interesting object, 

 with the fringed mantle. It is found alive in great quan- 

 tities in the autumn and spring, at low tide, attached to 

 stones and other shells ; and, in the dead state, is strewn 

 on every sandy shore both here and in Europe. I have 

 often used it alone, or mixed with pebbles, as a bottom to 

 my tank. 



