_Genus_--BALANUS.
Fig. 1 _a_ and 1 _b_, Balanus spongicola, external views of
scutum and tergum; 1 _c_, _var._ of the tergum, from a
specimen from the Cape of Good Hope; 1 _d_, _var._ of the
tergum from the West Indies.
2, Balanus lævis.
2 _a_, " " fossil, elongated _var._, showing
lower part of basal cup filled
up with a cancellated mass.
2 _b_ and 2 _c_, " " scutum, external and internal view
of.
2 _d_ and 2 _e_, " " scutum (_variety_), internal and
external view of.
2 _f_, " " scutum (_variety_), external view.
2 _g_, " " tergum, external view.
3 _a_, Balanus perforatus, scutum, internal view; 3 _b_,
tergum, internal view; 3 _c_, tergum, _var._ external view.
4 _a_, Balanus concavus (_var._ from Panama), scutum,
internal view; 4 _b_, scutum, external view; 4 _c_, tergum,
external view; 4 _d_, tergum, fossil, Coralline Crag; 4
_e_, tergum, fossil, Italy.