aperture

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The Cheshire Cat is a fictional cat from Lewis Carroll's Alice's Adventures in Wonderland. (Alice in Wonderland)

11 Banned Books Through Time

United States electoral college map showing number of electoral votes by state.

How Does the Electoral College Work?

Close up of books. Stack of books, pile of books, literature, reading. Homepage 2010, arts and entertainment, history and society

12 Novels Considered the “Greatest Book Ever Written”

Close-up of tobacco plants in Ontario, Canada. Tobacco, Nicotiana, cured leaves used after processing in various ways for smoking, snuffing, chewing, and extracting of nicotine.

7 of the World’s Deadliest Plants

Lusitania sinking, illustration from The War of the Nations (New York), December 31, 1919. World War I, WWI. This image is one of three on the page. (See source file for the other two.)

7 of the World’s Deadliest Shipwrecks

Groups of depositors in front of the closed American Union Bank, New York City. April 26, 1932. Great Depression run on bank crowd

Causes of the Great Depression

Ahura Mazda - relief of the Zoroastrian god Ahura Mazda at the ancient ruins of Persepolis in Iran. Also known as Ormazd Zoroastrianism,

Which Religion Is the Oldest?

aperture

shell structure

Learn about this topic in these articles:

snails

In gastropod: The shell
…the last whorl is the aperture, or opening. The shell is secreted along the outer lip of the aperture by the fleshy part of the animal called the mantle, first by outward additions to the shell lip and then by secretion of inner thickening layers. The outer layer, or periostracum,…
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