126 THE NAUTILUS. 
firm than those of its brothers which flourish so finely in San Fran- 
cisco Bay. A slender curved specimen of Solen ensis, the length of 
one’s finger, is present from its home in the sands of the “Skagen,” 
while its little cousin S. pellucidus, is almost as thin and transparent 
as tissue paper. Quite the opposite from this are the heavy black 
shells of Astarte compressa from Greenland. This northerner seems 
heavily clad to resist the waves of his native region. 
The principal limpet is Patella vulgata, a large, heavy, conical 
shell, with a sharp apex and rather distinct ribs. There is also an 
oblong sea weed limpet, He/cion pellucidum. Naturally you will find 
Nassa reticulata present, a plump, checked shell about an inch in 
length ; also that sharp corkscrew Turritella terebra. . 
Macoma baltica is a thick shelled, short and stout little Dutchman, 
whose interior is as rosy as the coming of dawn, and whose very red- 
ness shines clear through its white exterior. There are other tellens, 
small, flat and thin, also some small top-shells of which Trochus 
cinerarius is chief. It is interesting to note that almost all the shells 
were named by the great Linné, and we are carried back to the 
cheery northland, where he explored and studied and wrote not for 
his time alone, but for future generations as well. 
Of freshwater shells there is the great Planorbis corneus, an inch 
and a quarter across, the little button-like P. umbilicatus, the thin- 
shelled, inflated Limnea ovata and that odd little three-cornered 
mussel Dreissena polymorpha. This shell is shaped like a large 
beechnut, and from one side comes out a byssus of fine black silk. 
Note what Woodward says of this little creature that has strayed 
from its home in southern Russia, and has even entered the iron 
water pipes of London. 
Helix pomatia, the great edible snail, adds two large shells to the 
collection. I have just obtained some live specimens of this species 
which were imported by San Francisco grocers, and intend to try to 
domesticate them. My Danish collection contains several other spe- 
cies of Helix, e. g., the well known garden snails, H. nemoralis and 
H. hortensis,so common in England. There are also several small 
forms, like Helix hispida and minute kinds like Zua lubrica. 
Finally there are specimens of the singular genus Clausilia, with 
their long slender, many whorled little shells, whose apertures are 
set with teeth, as if to keep the poor little creature inside his prison 
house, or more probably to keep his enemies out. 
