What is "mason shell"

Mason \Ma"son\, n. [F. ma[,c]on, LL. macio, machio, mattio, mactio, marcio, macerio; of uncertain origin.]

1. One whose occupation is to build with stone or brick; also, one who prepares stone for building purposes.

2. A member of the fraternity of Freemasons. See Freemason.

   Mason bee (Zo["o]l.), any one of numerous species of solitary bees of the genus Osmia. They construct curious nests of hardened mud and sand.

   Mason moth (Zo["o]l.), any moth whose larva constructs an earthen cocoon under the soil.

   Mason shell (Zo["o]l.), a marine univalve shell of the genus Phorus; -- so called because it cements other shells and pebbles upon its own shell; a carrier shell.

   Mason wasp (Zo["o]l.), any wasp that constructs its nest, or brood cells, of hardened mud. The female fills the cells with insects or spiders, paralyzed by a sting, and thus provides food for its larv[ae]

n. (context zoology English) carrier shell