Dictionary.net

Various marine crustaceans, free swimming in the larval state, but permanently fixed as adults; there are some 800 described species, grouped in several genera, including Lepas, Balanus, and Scalpellum.

[From the likeness to spectacles.] Pincers enclosing the muzzle of a horse, to keep him quiet for any slight operation; the Twitch (q.v.) is better.

Spectacles; (?) a corr. of binocle, as binnacle also is; or (?) connected with obsolete bernlein, of the same meaning; and this with beryllus.