The great heyday of mystery stories back in the 1930s and 1940s often had the setting take place in museums or around the exotic unknowns of Egyptian culture and the land of Egypt. That fiction is just as alluring today, however, some of the real mysteries found within museums of the past can be just as entertaining.

I once read about an extraordinary occurrence in the Natural History Museum in London, where two desert snails, whose scientific name is Helix destorum, were brought home from Egypt, where they had been in the possession of their finder for a number of years prior to arriving in England.

They were supposed to be dead, so they were fast gummed (glued) down, like other exhibits of the kind and time, to the usual tablets and left in their glass show case.

Five years passed with nothing to indicate the faintest flicker of life in either. Then chance led to an examination, and the discovery was made that one of the snails had been newly repairing the crust which closed the entrance to its shell.

Both snails were taken out and placed in tepid water. One revived and began repairing the lip of its shell which had been damaged in fixing it to the label.

Now, this little museum mystery wasn't by any means a great mystery. Snails have been found in the Sahara sands, where the day temperature was 122 degrees Fahrenheit, where no rain had fallen for five years.

Others kept without food or water for four years in a collector's drawer were placed in water and revived, and six months later one of them was the mother of thirty baby snails.

Thinking back on the sea for other mysterious natural treasures brings Limpets to mind. Here the shell is single, but conical, not a spiral like that of the snails and periwinkles.

There are many kinds but the common limpet is as interesting as any creature. By pressing its powerful sucker foot on the rock it gets such a grip that it can scarcely be detached by a direct pull. Sideways it may be suddenly wrenched from its grip, but not if it has warning of impending danger. Quite a feat for such a little creature!

Long ago there was a popular tale about a natural who took advantage of the lowly limpet to save his own life. Whether the story was true or not, it made for a good bit of illustration of the strength of the limpet. Here's what I know about it.

The naturalist had fallen into the sea in Scotland in a deep, rocky place out of which it was impossible to climb owing to the slippery steep rocks. Drowning seemed inevitable with the rising of the incoming tide. Fortunately he noticed some big limpets clinging to the rocks and he knew their power.

However, he made to make them aware that they were likely to be dislodged by sudden pressure. So he gave each of them a sharp tap in turn. They clung with all their night and main and he climbed up on them, using them as stepping stones to safety.

I'm not saying that happened because I wasn't there, because strange things are often true. What I do know is that the limpet secures its hold not only by means of its great muscular foot, but also somehow it manages to scrape or erode in the rock a hole exactly matching the outline of its shell. Whether this is done by a cutting action or by the aid of an acid which the creature secretes, is not certain, however the acid theory has high authority for acceptance.

For the limpets to stick is a proverbial performance, but they do not remain stuck. They move with each tide, down the rock to scrape off with their tongues the fine weeds growing on the stones. Then each limpet returns to its own niche, never mistaking it for anothers.

It would be useless to attempt to invade another limpet's home, for no two are exactly alike, and each must fit into its own retreat. Yet the real mystery and backbone to the truth about limpets is that every common limpet is blind!

Wentle-traps who are very beautiful of shell come to mind when I think of the mystery of Mother Nature's coloring book. There are also Murices, which bore through the shells of other mollusks and secrete a fluid which gave the ancients their famous Tyrian dye. Then there are Whelks, which tunnel the shell of the unfortunate oyster.

Can't forget the Periwinkles which teem among the seaweed and other vegetable debris between high and low tide. Another is the Cone-shells, remarkable for beauty and of high value in the market of shells -- these and scores of other species are in the same group -- the Cowries of tropical waters.

No more lovely coloring is to be found than among the Cowries, though why such charms should be lavished on their shells is not obvious, for the fleshy mantles cover a great part of the shells. Then those mantles again are of the richest hues of color, an extravagance of rival charms of hue competing in the same mollusk.

Primitive cultures have long used the cowries as money, but at one time they had the value as equivalent of gold for more years than history is able to recount.

Beautiful natural architecture and coloration are found again among the Wing-shells and the Fountain-shells.

The fountain shells, who can be four or five pounds in weight, were ground to make porcelain, or often used to make cameos.

Helmet snails were also taken from the sea to serve the cameo cutter too, while the Tritons served the Romans as a trumpet, and in the South Sea Islands that have been long used as a war clarion in native ceremonies.

The most notorious of all the mollusks, is their kin, the Nautilus, the sole survivors of a race with which the seas once teemed. The nautilus possesses a shell and lives in its outermost chamber, not in the whole of it.

The foot round about the mouth has numerous tentacles which can be withdrawn into shields.

In its youth, the nautilus occupies a shell shaped like a horn, but as it develops, the shell becomes a chambered spiral, and the fleshy body, continually drawn toward the opening, leaves the earlier parts of the shell.

the later developments wind around and enclose the earlier, and the central chambers of the shell become filled with a natural gas.

The exterior of the shell is covered with a thin membrane which is removed when the animal has been caught, to reveal a substructure of sheeny mother-of-pearl.

Ancient tradition attributed to the nautilus the power of raising its arms to the wind and swimming with them as sails.

Poets and others remember the legend and still accept it as truth. The fact is that the nautilus propels itself through the sea by squirting out water in the same manner as a cuttle.

 These drawings of shells of land, sea, and river only show a small portion of the wonders of little workers in their humbly built homes.  Laid out the drawings do not, of course, show the shells in their natural sizes, but reduced.

The Paper Nautilus is a different animal. only the female here has a shell. It exists simply as a cradle for her eggs, one of the loveliest cradles in the world, a charming evidence of the care and genius, we might say.

This is one of Mother Nature's finest examples in providing for the safety and well-being of the defenseless young of a species.