38 CALIFORNIA SEA-SHELLS. 



scar, within the shell, is very evident. This 

 species is thick and solid, white, more or less flat- 

 tened and distorted, with rough lines of growth 

 and indistinct radiations. Breadth, from one- 

 half to three-quarters of an inch. The members 

 of this genus build a shelly layer under the foot, 

 which also shows the peculiar muscle-scar. 

 There is a good deal of uncertainty respecting 

 the number of our California species, as they arc 

 variable in appearance in the different stages of 

 growth, and different species appear to run into 

 each other. These doubtful questions present 

 a good field for study. 



Seurria mitra, Esch., Fig. 2, PL X, has a pure 

 white, conical shell, which is sometimes worn as 

 the drop of an ear-ring. It is said to live on the 

 roots of seaweeds. I found one living specimen 

 on a rock, at extreme low tide. It can easily be 

 distinguished from other shells, by its sharp con- 

 ical form, pure white color, and nearly circular 

 outline. Dead shells are common on the beach ; 

 common length, one inch. 



Xacella incessa, ITds., Sea-weed Limpet, Fig. 

 3, PI. X, lives on sea-weeds. It is oblong, coni- 

 cal, horny in appearance, brown, thin, one-half 

 to three-fourths ot an inch in length. 



Most of the limpets live near the shore, be- 

 tween high and low water marks. Almost all of 

 our species may he collected with moderate 

 pains; many of them are very pretty, and they 

 have one advantage for the collector, namely, 

 they are easily cleaned. They may be dislodged 

 from the rock by a sudden lift, with a broad blad- 

 ed knife, but it previously disturbed, they cling 



