Snail
3 of the 7 encyclopedias on this shelf carry an entry for Snail. Both are reproduced below, so you can see where they agree and where they differ.
Aiton's Encyclopedia (1910)
a common name for a number of mollusks. They are chiefly terrestrial, carrying their shells on their backs and creeping slowly by means of a sucker-like projection or foot, in some species covering the whole side of the body. There are over 5,000 species. The head of the garden snail is furnished with four stalks, two long and two short. At the tips of the long ones are black knobs, the "stalked eyes" of the snail. Most land snails breathe by a single lung. The lung opening may be seen. The shell of a snail is of interest. The pointed end is the apex. The large opening is the aperture. The edge of the aperture is the lip. The spiral groove on the outside, running to the apex, is called the suture. The turns of the shell between the grooves are called whorls. The whorls, all taken together, excepting the largest or body whorl, constitute the spire. Hold the apex up, the aperture toward you. If the aperture is toward your right hand, it is a dextral or right-handed shell. If towards your left hand, it is a sinistral shell. The food of the snail is green leaves and the like. The tongue is red and is roughened like a rasp. The egg of a snail is large and is surrounded by jelly which the young snail does not leave till it has a tiny shell of its own. The shell of a snail is made and mended by a juice from the body which is at first sticky and hardens into shell. We have two common forms of snail shells, one simply coiled, the other twisted. We have sixty to seventy-five different species in the United States . The Romans made a specialty of snails for table use. The edible snail of southern Europe, still used for food, is as large as an apple. Snails fattened in Switzerland are sent to the Vienna market. They are eaten in the season of Lent. Snail soup is served in the restaurants of Paris. Slugs are very much like snails, having, however, only a vestige of a shell. When extended, the various species measure from one to three inches in length.
Collier's New Encyclopedia (1921)
the common name of gasteropodous mollusks comprising the numerous family Helicidæ. They feed chiefly on vegetable substances. The mischief which they do to garden crops is too well known. Snails delight in warm, moist weather; in dry weather, their chief time we of activity is during the night, and they hide themselves by day; but after rain they come forth at any hour in quest of food. At the approach of winter or in very dry weather they close the mouth of the shell with a membrane (epiphragm), formed by the drying of the mucous substance which they secrete, and become inactive and torpid. Snails retreat into crevices for the winter, or into holes which they made in the earth, and which are roofed over with earth, dead leaves, etc., agglutinated by secreted mucus. The great vine snail, or edible snail (Helix pomatia), a European species, was considered by the ancient Romans one of their table luxuries. In some countries, as Switzerland and parts of France, they are cultivated for the table.
American Watchmaker and Jeweler (1892)
A cam resembling a snail in form, used in the striking attachment to clocks.