Spirula
Date 1882
Source Popular Science Monthly Volume 21
Author Unknown
Source: https://commons.wikimedia.org/wiki/File:PSM_V21_D782_Spirula.jpg

The ram's horn squid, little post horn squid or tail-light squid (Spirula spirula) is a species of deep-water squid-like cephalopod mollusk. It is a deep-ocean dweller. The shell of Spirula is extremely light in weight, very buoyant, and surprisingly durable; it very commonly floats ashore onto tropical beaches all over the world. This seashell is known to shell collectors as the ram's horn shell or simply as Spirula.