Valvæ 3, 5, aut 7, approximatæ; carina solùm ad basales apices tergorum extensa, termino basali aut truncato aut in discum profunde infossum producto; scuta pænè ovalia, umbonibus ad angulum rostralem positis.
3. Genus—DICHELASPIS, Darwin. (‘Lepadidæ,’ p. 115.)
Valvæ 5, quæ ferè pro septem haberi possent, scuto in segmenta planè duo, ad angulum autem rostralem conjuncta, diviso; carina plerumque sursum inter terga extensa, deorsum aut disco infosso aut furcâ aut calyce terminata.
4. Genus—OXYNASPIS, Darwin. (‘Lepadidæ,’ p. 133.)
Valvæ 5, approximatæ; scutorum umbones in medio marginis occludentis positi; carina rectangulè flexa, sursùm inter terga extensa, termino basali simpliciter concavo.
5. Genus—CONCHODERMA, Olfers. (Darwin, ‘Lepadidæ,’ p. 136.)
Valvæ 2 ad 5, minutæ, inter se remotæ; scuta bi- aut tri-lobata, umbonibus in medio marginis occludentis positis; carina arcuata, terminis utrinque pæne similibus.
6. Genus—ALEPAS, S. Rang. (Darwin, ‘Lepadidæ,’ p. 156.)
Capitulum aut sine valvis, aut scutis corneis, pæne abditis.
7. Genus—ANELASMA, Darwin. (‘Lepadidæ,’ p. 169.)