scuta

Operculum, or opercular valves.These consist of a pair of scuta and a pair of terga.

Cirripedia without a peduncle; scuta and terga furnished with depressor muscles; other valves united immoveably together.

Altogether the scuta and terga are attached, as far as muscles are concerned, to the shell and sack, by three longitudinal pairs.

This articulation of the scuta and terga is prefigured amongst the Lepadid, in Pollicipes mitella, and in Lithotrya.

In shape the scuta are generally sub-triangular; but in some species of Pyrgoma and in Chelonobia, &c. they are much elongated.