The scuta and terga are much more elongated, a scutum being here 35/1000ths of an inch in length.
The scuta, terga, and carina are much larger than the other valves.
scuta: narrow, with the upper part produced; not striated longitudinally; coloured by a pale purple, longitudinal band.
Operculum, or opercular valves.These consist of a pair of scuta and a pair of terga.
scuta, of the usual sub-triangular shape, and not transversely elongated, as in T. purpurascens.
Cirripedia without a peduncle; scuta and terga furnished with depressor muscles; other valves united immoveably together.
In shape the scuta are generally sub-triangular; but in some species of Pyrgoma and in Chelonobia, &c. they are much elongated.
This articulation of the scuta and terga is prefigured amongst the Lepadid, in Pollicipes mitella, and in Lithotrya.
scuta, with the basal segment narrower than the occludent segment, and about half as long as it.
Altogether the scuta and terga are attached, as far as muscles are concerned, to the shell and sack, by three longitudinal pairs.