On hard seafloors, crawling gastropods have coiled shells or flat, saucer-like shell cases that allow them to retreat into the shell when in danger.
(crawling gastropods; have coiled; shells or flat, saucer-like shell cases that allow them to retreat into the shell; T:On hard seafloors) (shells or flat, saucer-like shell cases; allow; them to retreat into the shell when in danger) Context(shells or flat , saucer - like shell cases allow,List([51, 101))):(them; to retreat; into the shell; T:when in danger)
shells or flat , saucer - like shell cases allow,List([51, 101))
crawling gastropods shells or flat, saucer-like shell cases them
have coiled allow to retreat
shells or flat, saucer-like shell cases that allow them to retreat into the shell T:On hard seafloors
them to retreat into the shell when in danger
into the shell T:when in danger