66 THE NAUTILUS. 
above locality also, square yards of surface of some of the flat 
rocks being filled with its shells. This species seems to abound 
from San Pedro, Cal., to Magdalena Bay, Baja Cal., where I 
found millions of the young shells in the drift (determined by 
Dr. Dall). 
Acmaea patina cumingii.—This is the commonest species at 
Bird Rock and all along our coast, but seems to have been over- 
looked by Smith and Bailey. 
Tegula ligulatum.—One of the commoner shells on all our 
beaches. 
Pecten hastatus.—In kelp holdfasts washed ashore at Pacific 
Beach. 
Pecten hericeus.—Valves frequent in the drift. 
Phacoides californicus.—Frequent in the drift on all our 
beaches. 
Phacoides richthofeni.—Valves occasionally washed ashore. 
Mr. Emery found it living in False Bay. 
Fissurella volcano.—This is probably one of the most abundant 
and widely distributed species on our coast. I have generally 
looked with contempt on the gathering of dead shells; but for 
lack of better material I have gathered several thousand of this 
from the drift, from very minute to specimens of maximum 
size. It occurs from Monterey, Cal., south at least as far as 
Salina Cruz, Oaxaca, where I have collected it in abundance. 
The beach-worn shells show a beautiful diversity of color not 
observable in the living shells. About fifteen per cent. of the 
shells picked up at La Jolla are of the var. crucifera Dall, some- 
times the arms of the cross extending only halfway down the 
sides of the shell, sometimes wholly worn away at the apex, 
often one or more arms missing; in young specimens, say 2 mm. 
long, frequently only the lateral white arms appear halfway to 
the lower margin of the shell. The ground work is usually 
reddish, the gray or black forms being much rarer. From the 
four white arms of var. crucifera there occurs every variation in 
number up to 20 or 30 or more, the red rays on a white ground 
—like red-hot lava flowing down the sides of a mountain, hay- 
ing given it its name. This is probably the typical form. 
Acmaea triangularis.—One specimen detected in the drift on 
the beach. 
