178 New York State Museum 



that it can not swim away from the oyster. It is unneces- 

 sary to touch further upon these associations. Those that 

 have been given are quite suggestive. 



Distribution of the Mollusks 



From the above discussion of the animal associations 

 along our coasts the reader should gain some idea of the 

 geographical distribution of the representatives of the 

 various groups. The mollusks along our shores and the 

 mollusks, together with brachiopods, among fossils will 

 probably attract most the attention of the beginner. It 

 therefore would seem worth while to give a short survey 

 of their distribution and the conditions that influence it. 

 As we have seen, nearly every conceivable type of sea 

 bottom or coast line between tides has its own peculiar 

 type of molluscan life. There are borers in the rocks 

 and borers in the shells of other forms. Some groups 

 prefer to live on rocks above low-tide mark and here we 

 find such forms as the Periwinkles, the Rock Snails, the 

 Trochids, and the majority of the forms with patelliform 

 (limpetlike) shells. Forms like the English Whelks, 

 Stimpson's Sipho, and the Ten Ribbed Snail have a fond- 

 ness for rocky or gravelly ground below low-tide mark ; 

 other mollusks prefer sandy bottoms ; still others burrow 

 in the mud. There are hosts of species that seek their 

 homes in the tangled masses of seaweed or other vege- 

 tation etc. 



It has been found that the temperature of the water 

 rather than its depth appears to influence the distribution 

 of marine life. In the discussion of mollusks of the dif- 

 ferent associations it has been pointed out here and there 

 that certain cold water or arctic species that live in the 

 shallow waters of the more northern coasts are found in 



