In biology, a
lorica is a shell-like protective outer covering, often reinforced with sand grains and other particles that some
protozoans and
loricifera metazoans secrete. Usually it is tubular or conical in shape, with a loose case that is closed at one end. An example is the protozoan genus
Stentor, in which the lorica is trumpet-shaped. In the
tintinnids, the lorica is frequently transparent and is used as .
Halofolliculina corallasia has a lorica that is attached as an outer structure, and into which it retracts when disturbed.