What is "acmaea testudinalis"

Limpet \Lim"pet\ (l[i^]m"p[e^]t), n. [Prob. through French fr. L. lepas, -adis, Gr. lepa`s, -a`dos.] (Zo["o]l.)

1. In a general sense, any hatshaped, or conical, gastropod shell.

2. Any one of many species of marine shellfish of the order Docoglossa, mostly found adhering to rocks, between tides.

   Note: The common European limpets of the genus Patella (esp. Patella vulgata) are extensively used as food. The common New England species is Acm[ae]a testudinalis. Numerous species of limpets occur on the Pacific coast of America, some of them of large size.

3. Hence: Somthing or someone that clings tenaciously to another object or person; specifically a military explosive device having magnets allowing it to cling to a metallic target object, such as the hull of a ship.

   3. Any species of Siphonaria, a genus of limpet-shaped Pulmonifera, living between tides, on rocks.

4. A keyhole limpet. See Fissurella.