clionidæ

from The Century Dictionary.

• A remarkable group of the Porifera or Spongida, the boring sponges, having no fibrous skeleton, but provided with peculiar silicious spicula, by means of which they can burrow into the shells of the mollusks upon which they are parasitic. They existed in the Silurian epoch.
• A family of gymnosomatous pteropods, typified by the genus Clione, to which different limits have been assigned.