cowry

せっかくThe Shell Collectionを読んでいるので一つ位は貝の名前を覚えたいと思っていますが、その一つが出て来ました。
There were many such discoveries: a small horseshoe crab mounting a larger one in the wavebreak, a fistful of mussels clinging to the damp underside of rock. But it was wading ankle deep, when his toes came upon a small round shell, no longer than a segment of his thumb, that the boy truly was changed. His fingers dug the shell up, he felt the sleek egg of its body, the toothy gap of its aperture. It was the most elegant thing he'd ever held. "That's a mouse cowry," the doctor said. "A lovely find. It has brown spots, and darker stripes at its base, like tiger stripes.
"mouse cowry" は貝の名称とは思えませんが、辞書には "cowry" の説明が次のように書かれています。
・Oxford English Dictionary: A marine mollusk that has a smooth, glossy, domed shell with a long narrow opening, typically brightly patterned and popular with collectors.: The flattened yellowish shell of the money cowrie, formerly used as money in parts of Africa and the Indo-Pacific area.
・Cambridge English Dictionary: a small sea creature with a soft body and a brightly coloured shell, or the shell itself used in the past as money in parts of Africa and southern Asia: a cowrie shell
どうやら "cowry" は宝貝のことを指しているようです。"mouse cowry" はその "cowry" の一種でネズミほどの大きさがあるのでしょう。
Wikipediaにはどちらの説明もあり、"mouse cowry" で検索するとMuracypraeaの項目に転送され、次の説明と写真が掲載されています。（以下は抜粋）
Muracypraea mus, common name the mouse cowry, is a species of sea snail, a cowry, a marine gastropod mollusk in the family Cypraeidae, the cowries.
The shells of these rare cowries reach on average 38--45 millimetres (1.5--1.8 in) of length, with a minimum size of 30 millimetres (1.2 in) and a maximum size of 67 millimetres (2.6 in). They are pyriform, quite thick and heavy, almost swollen, with slightly square contours. The dorsum surface of these smooth and shiny shells is generally pale brown or beige, with a variable pattern of dark brown spots.
ネズミほどは大きくないですね。