kw: natural history, natural science, museums, collections, photographs
The species is Turbinella angulata (Lightfoot, 1786), also known as the West Indian Chank Shell; "chank" comes from a native word for "divine conch". This specimen is a Pliocene fossil collected in Florida, so the animal lived about 5 million years ago. The species is still found in waters off Florida and around the Caribbean and the western Atlantic Ocean.
The many holes in the shell are from calcium-consuming organisms that gradually destroy any shell left lying on the bottom long enough. When you find a shell, or a piece of one, that is ragged and full of holes, it has been on the sea floor for several years or decades. This specimen and those with it were sitting around for some time before an underwater mudflow covered them and preserved them so they could "hang around" a few million years until erosion exposed the fossil beds known as "marl pits" in southern Florida.
This particular specimen has a chunk knocked out, as you can see at the right. This allows us to view the columella, the central structure that supports the whorls of many snail shells. I gave the shell a quarter turn and played around with light and focusing until I could get a picture of part of the columella, seen here:
The largest shells of this species are more than a foot-and-a-half long, only a little smaller than the largest American snail, the Florida Horse Conch (which is not really a conch; we can dig into that another time).