Fig. 104; TEN-RIBBED SNAIL. Massachusetts Bay. 



MpLLUSKS 145 



literally covers the rocks on many parts of the New England coast 

 north of Cape Cod. It is most abundant between tides, where the 

 rocks are covered 

 with barnacles up- 

 on which it feeds. 

 It ranges from 

 Montauk P o i n t, 

 Long Island, to 

 the Arctic Ocean, 

 and is abundant 

 on the European 

 coasts as far south 

 as Portugal. Witli 

 us it grows to 

 be about one and 

 one-lialf inches 

 long but becomes larger on the northern coasts of Europe. 



It is very variable in form and color. Some individuals are 

 quite smooth while others are ringed Avith deep ridges, or have 

 rough, scale-covered shells. Some are dark brown, others white, 

 gray, yellow, dull orange or ringed with combinations of these col- 

 ors. The snails which live upon insolated rocks far off the coast, 

 exposed to the full force of the ocean, are small, and are dark gra)'^ 

 in color with dull yellowish bands. Those living on the rocks of 

 protected shores are more variable, both in form and color. 



The eggs are laid during the summer in little spindle-shaped 

 yellow capsules which resemble minute ten pins set up on their 

 pointed ends. They are placed on the nnder sides of rocks, or on 

 dead shells. (Fig. ^94). 



A closely related species (Purpura patulaj from the Mediter- 

 ranean Avas used to make the Tyrian purple dye used by the Ro- 

 mans for their ceremonial togas. The snails were pounded in a 

 mortar and mixed with water and soda. After a few hours the liquid 

 changes from yellow to deep purple, and may then be used to dye 

 wool or cloth. 



The Ten-Ribbed SnaU, fChrysodomus decemcostatus, Fig. 104 J, 

 becomes fully three inches in length. It is yellow-brown in color, 

 and displays ten whorled ridges. It is found off the New England 



