Thanks to John Huntley for the tip. In the Introduction of the book Conchophilia (Princeton University Press), the authors wax poetic and philosophical as they reflect on the life of shells and their liminal nature:

“Indeed, there is something particular about shells as liminal things, objects that hover between life and death, and that throw our thoughts into far places, not least from whence they came. Shells are things that were once inhabited by creaturely life, that once belonged to an ecosystem distant from humankind before finding their way into the artist’s studio, or the drawers of a collector’s cabinet.”