Philinacea
<em>Philinacea</em>
Philinacea
The former Philinacea are (2011) part of the superfamily Philinoidea of Opisthobranch sea slugs. (See links below for current taxonomy.)
The families Cylichnidae and Scaphandridae have external shells into which they can partly withdraw.
The family Philinidae have completely enclosed fragile shells (partly exposed in Philine denticulata).