Valvæ testæ 4; interdum inter se externè confluentes: parietes poris perforati, multis plerumque seriebus; basis plana, irregularis, calcarea aut membranacea.
4. [Genus—ELMINIUS], Leach. (Darwin, ‘Balanidæ,’ p. [345].)
Valvæ testæ 4; parietes non porosi; basis membranacea.
5. [Genus—PYRGOMA], Leach. (Darwin, ‘Balanidæ,’ p. [354].)
Valvæ testæ in unam confluentes; basis cyathiformis aut subcylindrica, coraliis affixa.
6. [Sub-Genus—CREUSIA], Leach. (Darwin, ‘Balanidæ,’ p. [375].)
Valvæ testæ 4, radiis instructæ; basis cyathiformis, coraliis affixa.
7. [Genus—CHELONOBIA], Leach. (Darwin, ‘Balanidæ,’ p. [382].)
Valvæ testæ admodum crassæ, 6; sed ex iis, valva rostralis intùs è tribus valvis rudimentariis conjunctis constat; basis membranacea; scuta angusta, tergis cristâ articulari corneâ conjuncta.