If you guess shells and seashells your technically correct, but graydaysandcoffee nailed it as a Conch Shell. Here are the originals only slightly cropped.
I joined a local amateur photo association. Last night we had a photo workshop in which i participated. I focused, literally, on timed exposures and learning manual focus. Most stations were set up to shoot in a darkened room with different lighting options. For these photos, I simply placed the conch shells under an incandescent lamp and decided to try my 14mm macro extension.
You all receive my warmest congratulations.