18 
CALIFORNIA SEA-SHELLS. 
inches long, the spire consisting of five or six in- 
distinct whorls, cut into waves by shallow furrow* 2 . 
Spiral lines, numeious ; 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, small 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 term 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 canaliculata, Duel., Grooved Purple, 
Fig. 5, PI. 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 
