There are a few different options for synonyms to describe something as being "spiral-shelled," or possessing a spiral-shaped shell. One possible term is "coiled," which suggests a tight, circular shape. Another option is "spiraled," which emphasizes the swirling, twisting nature of the shell's shape. "Helical" is a more technical term that describes something that follows the shape of a spiral; it can also be used to describe other spiral-shaped objects. Finally, "gastropod" is a term that specifically refers to a type of mollusk with a spiral-shaped shell, such as a snail or a conch.