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The reproductive organ of animals of the order squamata (lizards and snakes). It is two sided, allowing the animal to reproduce from either side. This is especially useful to snakes, as they have no legs to assist in mounting. The hemipenis is barbed, order to prevent the escape of the female and to keep the two animals connected in the act of fornication.

To answer a common question related to the hemipenis, no, snake and lizards have NEVER fornicated in threesome.
I can never eat lox and bagel again because the snake's hemipenis looked like smoked salmon with barbs.
by MazurkaMatt May 26, 2006