NOXIOUS AND VALUABLE ANIMALS. 361 



the common clam for fish bait has already been mentioned. The 

 Crustacea are all welcomed by the fish in a similar manner. To these 

 we may add the Squid (Loligo illecehrosa) and the various jointed 

 worms (Annelida) which live in the sand of the shore, some of which 

 are a foot or more in length. 



The King-Crab, or Horse-shoe, {Lbnulus polyphanus,) is em- 

 ployed as food for hogs ; and many of them are speared by boys for 

 this purpose, and sold for half a cent apiece. It is also regarded as 

 excellent bait for eels. 



3. Such as are employed in agriculture and the arts. In agricul- 

 ture, the solid parts of the MoUusca, their shells, are employed on 

 account of the lime which forms their basis. One of the most useful 

 forms in which they are found for this purpose, is the shell marl. In 

 Berkshire County this marl is found in considerable quantities. It is 

 formed of the small, fresh-water shells which have subsided to the 

 bottom, and, mingling with the fine mud, become consolidated. This 

 process is every day going on. In a few specimens which I have ex- 

 amined, 1 have detected Planorhis Mcarinatus, P. campanuldtus, P. 

 parvus, Physa heterostropha, Valvdta tricarindta, Limnda hiimilis ? 

 and Cyclas dubia, shells which are now everywhere found in the 

 streams of Massachusetts. 



Shell lime is very much used in many parts of the world, and in 

 some of the United States, as an ingredient in composts, and for dress- 

 ing grain lands ; but it has not yet become so extensively employed in 

 Massachusetts as would be profitable. Some little diversity of opinion 

 has arisen as to the utility of lime in improving wheat crops. It has 

 been stated by good farmers, that they have dressed their fields freely 

 with lime, without any manifest improvement of the crop ; while the 

 next year, when no lime is applied, the crop has been ample. Such 

 statements would seem to discourage the use of lime for grain crops. 

 Dr. C. T. Jackson, who has paid great attention to agricultural chem- 

 istry, offers an explanation to this seeming evidence against the utility 

 of lime. He says, that where lime is spread with freedom, it will not 

 form its combinations with the soil so as to be of benefit during the 

 first season ; but that on a second season its effects will be abundantly 

 apparent. 



Shell lime is preferable to stone lime in agriculture, because it is 

 sure never to contain magnesia, which is always prejudicial to the soil, 

 and which is often a component part of stone lime. 



46 



