In this poem Oliver Wendell Holmes is glorifying the chambered nautilus and mourning the death of a single representative of the species. In the first several verses, the nautilus is compared to a “ship of pearl,” sailing through “gulfs enchanted.” This metaphor allows us to understand what is meant by the description “webs of living gauze” (compare this to its “purpled wings” in the first verse). The gauze is a reference to the canvas from which the sails of ships are made, another instance of comparison between the nautilus and a man-made vessel. It could also be a reference to the white tentacles of the body of the creature that sometimes protrude from the shell, forming a thick curtain possibly resembling a web.
The first and second verses paint a picture of a tumultuous mythological setting in which the ship is “wrecked” – those “webs of living gauze no more unfurl,” and the nautilus is dead. Not only is it dead, but it has been crushed, and it’s body, which dwelt inside the shell, has been exposed:
And every chambered shell
Before thee lies revealed,
It’s irises ceiling rent, its sunless crypt unsealed!