From Longman Dictionary of Contemporary Englishseashellsea‧shell /ˈsiːʃel/ noun [countable] 
HBAthe empty shell of a small sea creature jewelry made out of seashells
HBAthe empty shell of a small sea creature jewelry made out of seashellsExamples from the Corpus
seashell• seashells on the beach• Or did you bag walnuts or avocados, seashells or pinecones, and sell them from your front lawn?• Those early cards were works of art, elaborately painted and trimmed with lace, jewels, feathers, seashells and tassels.• There was no rattle, as of seashells in a jar, and nothing came rolling on to the towel.• Also herbarium and a collection of seashells.• The projection from a semi-circle is reminiscent of certain forms of seashells.• Read in studio Art critics are being blamed for vandalising cast iron sculptures which have been likened to ice-cream cones or seashells.• Down below were the pink seashell murals lit by fluorescent lights, and distant black and white movies on the screen.• It sounds like a jar of small seashells. 