PERIWINKLES. 29 



tare is purple. Both of these species are very 

 interesting for study. They can easily be ex- 

 amined in little tide pools, while in motion, and 

 their method of clinging to the rock when the 

 water has left them should he noted. A near 

 relative to the above is the little Lacuna unifas- 

 ciata, Cpr., or Chink-shell, represented in Fig. 

 I, PI. VII. It is a very lictle thing, about one- 

 sixth of an inch long, very few whorled, brown 

 and glossy, with the color sometimes broken into 

 dots on the keel of the body whorl. The aper- 

 ture is semi-lunar, and the columella flattened, 

 with an umbilical fissure, from which it takes 

 its generic name. It is worth looking for. 

 Lacuna solidula, Lov., is sometimes halt an 

 inch in length, but often of less size. It is 

 three whorled, strong, smooth, with small um- 

 bilicus, brown surface and white columella. 



We have now come to the Trochidce or Top- 

 shells, one of the most prominent and numerous 

 families on the coast. They vary greatly in 

 many respects, but still have the family traits, 

 and family features. Some of them are the first 

 to greet you as you climb down the rocks to the 

 shore, others are rare and shy enough ; some 

 have little beauty, while others rival the rainbow 

 in their tints. They are mostly conical, with 

 entire apertures, and nacreous, or pearly, interi- 

 ors. When the outer coats are removed with 

 acids, the inner pearly layers appear. The ani- 

 mals feed on marine vegetation. We will begin 

 our description with the smallest species, Pliasi- 

 anella eornpta, Gld., Pheasant-shell, shown some- 

 what magnified in Fig. 3, PI. VII. It is BO small 



