Webster's 1913 Dictionary
SOFT-SHELL; SOFT-SHELLED
SOFT-SHELL; SOFT-SHELLED Soft "-shell `, Soft "-shelled `, a.
Defn: Having a soft or fragile shell. Soft-shell clam (Zoöl.), the long clam. See Mya. -- Soft-shelled crab. (Zoöl.) See the Note under Crab, 1. -- Soft-shelled turtle. (Zoöl.) Same as Soft tortoise, under Soft.
New American Oxford Dictionary
soft-shell clam
soft-shell clam (also softshell clam ) ▶noun a marine bivalve mollusk with a thin shell and a long siphon, valued as food on the east coast of North America. Also called soft clam, steamer. [Genus Mya, family Myidae, esp. M. arenaria. ]
soft-shell crab
soft-shell crab (also softshell crab ) ▶noun a crab, esp. a blue crab, that has recently molted and has a new shell that is still soft and edible. Also called soft crab.
soft-shelled turtle
soft-shelled tur tle (also soft-shell turtle ) ▶noun a freshwater turtle with a flattened leathery shell, native to Asia, Africa, and North America. [Family Trionychidae: several genera and many species, including the spiny soft-shelled turtle Apalone (or (Trionyx ) spinifera ) of North America. ]
Sanseido Wisdom Dictionary
soft-shell
s ó ft-sh è ll 形容詞 (脱皮後の )殻の軟らかい, 軟らかい殻 [甲 ]をもつ .
The Wordsmith Dictionary