220 WEST COAST SHELLS 



generally it is smooth. The size varies greatly, the 

 figure representing a fairly large specimen, though 

 occasionally an old one is found that is 

 much larger. 



Acmcsa incessa, Hds., the Seaweed 

 Limpet, Figure 215, is a common spe- 

 cies, and may be found living on the flat 

 central ribbons of the great seaweeds 

 Fig. 215 which are so conspicuous along the rocky 

 coast. The sides of the shell are flat- 

 tened and nearly smooth, and the apex is rounded. 

 The shell is of a dark brown color throughout, and 

 looks as if it were made of horn. It is seldom quite 

 so large as the picture represents. 



When the tide is low the huge plants to which 

 these shells are attached lie prone on the rocks, look- 

 ing like a pile of feather boas. Each one of them 

 has a very strong central rib, with numerous plumes 

 on either side. These are mingled with egg-shaped 

 air bladders, which serve to keep the upper parts of 

 the plant afloat when the tide is in. It is to this flat 

 and extremely tough central portion that the little 

 limpets love to cling, swaying backward and forward 

 with the swing of the billows. 



There are other seaweeds which help to cover 

 the rocks, the most common one being a stout, brown- 

 ish plant, sometimes called kelp, but whose real name 

 is Fi/ri/s. It is an exceedingly ancient organism, bemg 

 but little changed from plants that grew in the ocean 

 long before the time of man. Then there are others, 

 some of them red and others green ; this one, broad 

 and strong like a piece of leather, while its neighbor 



