18 CALIFORNIA SEA-SHELLS. 



inches long, the spire consisting of five or six in- 

 distinct whorls, cnt into waves by shallow furrows. 

 Spiral lines, numerous ; columella, enamelled ; 

 outer lip of a rich brown color within, with twen- 

 ty light ridges. The outside of the shell is gen- 

 erally covered with a whitish powder, which can 

 be removed, showing the dark brown shell. It 

 may be found alive, at low tide, on the surface of 

 rocks which are covered with coarse sea moss. 

 Operculum, sm?ll and- horny. 



One of the most common shell on this coast is 

 Purpura saxicola, Yah, The Rock Purple, 

 shown in Fig.- 4, PI. II. It derives its generic 

 name from the fact that the ancient Tyrians ob- 

 tained a purple dye from the bodies of a similar 

 species, while its specific name is peculiarly ap- 

 propriate, for it is ever found clinging to the 

 rocks, and hiding in their clefts. Length, less 

 than an inch ; spire, short ; columella , flattened ; 

 outer lips, thin ; canal, short ; umbilicus, small. 

 The inside is reddish brown, while the outside 

 varies greatly both in form and color. Sometimes 

 it is smooth and almost black, sometimes white 

 and coronated, but usually it is decorated with 

 double spiral bands of a dark color, often accom- 

 panied with spiral grooves. These many varieties 

 probably all belong to one species. It is found 

 on rocks which are covered only at high tide. 



Purpura canallculata^ Duel., Grooved Purple, 

 Fig. 5, PL II, is much more rare than the last 

 species, probably living in deep water. In size 

 it is about the same, but it is more smooth and 

 symmetrical. The spire consists of three whorls 

 with a deep suture between them. From apex 



