Its fragile shell was much prized by early conchologists for their collections, being so rare that it was said to be worth more than its weight in gold.

The visceral nucleus, which includes the liver, heart, gonad, sexual glands and kidneys, is a dark, stalked, triangular area protected by the shell, which also houses the gills.

It is uncommon in the Indian Ocean but more plentiful in warm waters off the western coast of North America.

Although its diet is varied, it feeds selectively on salps and doliolids, but also consumes arrow worms and copepods.

Other prey includes siphonophores, planktonic worms, fish eggs and larvae, and juveniles and smaller adults of its own species.