IV.] INTRODUCTION. lix 



dragon-fly. The innumerable host of marine Mollusca 

 afford a constant supply of food to sea-fowl of various 

 sorts, fish (especially the cod, haddock, mullet, gurnard, 

 halibut, and sole), crabs and other Crustacea, star-fishes, 

 sea-cucumbers, and Actiniae. No less than 35,000 spe- 

 cimens of a small bivalve [Turtonia minuta) were esti- 

 mated by Mr. Hyndman to be contained in the stomach 

 of a single mullet which had been taken in Lame Lough. 

 They are not even spared by their own kind. M. Des- 

 hayes fed some pet snails with chopped-up morsels of 

 one of their companions, which appeared to be unhealthy 

 and not likely to survive. Many instances of such 

 cannibal propensities in the land and freshwater Mollusca 

 will be found in this volume. Bulla lignaria is a great 

 tyrant among the smaller marine shell-fish, and uses the 

 strong plates of its singular gizzard to crush them. All 

 the whelk-tribe, as well as the Naticce, enfold their testa- 

 ceous prey in their large feet, and drill holes in the shells, 

 as before observed, in order to feed on their contents. 

 The great strength of the shells possessed by some whelks 

 does not save them from becoming victims in their turn. 

 I have been informed by intelligent fishermen, that,,jf 

 their lobster-pots (in which the Buccinum undatum is 

 often caught) are left a few hours longer than usual, the 

 shells of the whelks are found cracked ^' like nuts," 

 having been cleared out by the lobsters and crabs while 

 they were fellow-prisoners. Quantities of this kind of 

 whelk are caught on the Dogger-bank as bait for the cod- 

 fisheries of Iceland and Greenland. The way in which 

 gold-fish contrive to extract the animals from fresh- 

 water shells is curious. When the shell is too large to 

 be swallowed, the fish puts its mouth to it, and then, 

 sucking it for some minutes, lets it go. After a while 

 the snail recovers and withdraws itself from its shell, 



