126 THE NAUTILUS. 



firm than those of its brothers which flourish so finely in San Fran- 

 cisco Bay. A slender curved specimen of Solen en*i$, the length of 

 one's finger, is present from its home in the sands of the "Skagen," 

 while its little cousin 8. 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 Putilln m/i/fiin, a large, heavy, conical 

 shell, with a sharp apex and rather distinct ribs. There is also an 

 oblong sea weed limpet, He Icion pellucid um. Naturally you will find 

 Nassa reticiilafa present, a plump, checked shell about an inch in 

 length ; also that sharp corkscrew Turritella ierebra. 



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 Linne, 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 cornens, an inch 

 and a quarter across, the little button-like P. umbilleatiis, the thin- 

 shelled, inflated Limncea orata and that odd little three-cornered 

 mussel Dreissena polymorphic 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, //. in-nwrali and 

 H. hortensis, so common in England. There are also several small 

 forms, like Helix Itixpida and minute kinds like Zn<t lidn-i'-n. 

 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. 



