12 



BOLINAS BAY 



I dug out some of them, but gave most of my atten- 

 tion to the inhabitants of the rocks. 



Turning back the masses of olive green Fiicus^ 

 that most ancient of sea-weeds, I found a considerable 

 number of mollusks with shells like the one shown in 

 Fig. I. It is not a very common species for Califor- 

 nia, but is more abundant to the north, about Van- 

 couver's Island and southern x^laska. 



The shell of a full-grown specimen is an inch and 

 a half long. It is spindle-shaped, that is, it is largest 

 in the middle, and tapers to- 

 wards each end. There is an 

 opening on the right side of the 

 shell, extending about half way 

 to the apex or point. This 

 opening is called the aperture, 

 and is marked ap. 



This aperture is sometimes 

 called the mouth of the shell, 

 though it is in no sense the 

 mouth of the animal ; but since 

 it has been called the mouth, 

 the sides of the shell which 

 bound it are called lips. The one towards your right 

 hand is the outer lip^ and is marked o.L; the inner 

 lip is usually so grown to the central axis of the shell 

 that it is not distinct from this part round which the 

 shell seems to revolve, and which is called the 

 columella . 



At the lower end of the aperture is a little curved 

 canal^ marked ca. in the figure. 



Many shells do not have this canal, but have an 

 oval or nearly circular opening. The animals which 

 have shells with canals are mostly carnivorous, while 



Fig. 



~<:a. 



