MOLLUSKS 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 Point, 
Long Island, to 
the Arctic Ocean, 
and is abundant 
on the European 
coasts as far south 
as Portugal. With 
us it grows to 
be about one and 
one-half 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 with 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 gray 
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 under sides of rocks, or on 
dead shells. (Fig. 94). 
A closely related species (Purpura patula) from the Mediter- 
ranean was 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 Snail, (Chrysodomus decemeostatus, Fig. 104), 
becomes fully three inches in length. It is yellow-brown in color, 
and displays ten whorled ridges. It is found off the New England 

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