cassidulidæ

from The Century Dictionary.

• A family of exocyclic or petalostichous echinoderms, or irregular sea-urchins, known as heart-urchins, having a rounded or oval form, very fine spines, and no fascioles. It includes the subfamilies Echinoneinæ and Nucleolinæ.
• A family of proboscis-bearing pectinibranchiate gastropods, typified by the genus Cassidulus.