OLIVE SHELLS. 23 



Lies the last, but is much smaller, being only 

 three-fourths of an inch in length. Its whorls are 

 beautifully rounded and cut into little squares. 

 Shell, thin, light brown, with a trace of orange 

 inside. It is found from San Francisco Bay, 

 southward. 



N asset mcndica, Gld., Fig. 4, PI. IV, is a vari- 

 able shell, about the same in length as the last, but 

 more slender. The surface is marked with fine 

 spiral lines and numerous transverse ribs. Its 

 color is light brown, with a white " peristome," 

 or margin of the aperture. Fine specimens of 

 this species have been found at Santa Cruz and 

 Monterey. 



Nassci Cooperi, Fbs., Cooper's Basket-Shell, 

 shown in Fig. 5, PI. IV, is a pretty, brownisb 

 little shell, found from Bolinas Bay to San 

 Diego. It is spirally marked, like N. mendica, 

 but its ribs number only seven or eight to a 

 whorl, and are quite, high, giving the shell a 

 tubercled appearance. The white lip is marked 

 internally with small teeth. 



We now come to one of the beauties of our 

 Coast, the Purple Olive, Olivella biplicata^ Sby. 

 Fiir. 7, PI. IV. Every one must admire its blu- 

 ish-white, polished surface, and purple mouth. 

 The spire is short, with a distinct spiral groove 

 separating the w r horls. The inner w^all of the 

 aperture is marked by a bulge of enamel above, 

 and two small folds beneath, which give the 

 shell its specific name. Beds of living Olives 

 can sometimes be found just beneath the surface 

 of the sand, at low tide. They are active little 

 burrowers, throwing up little ridges as they 



