Shell varying from pink to blackish purple, often striped and ribbed longitudinally: orifice generally entire, sometimes toothed. Scutum with the articular ridge broad and reflexed. Tergum with the basal margin generally forming a straight line on opposite sides of the spur.

Var. (1) communis (Pl. [1], figs. [a], [b], [f supra]; Pl. [2], figs. [1 a], [1 c], [1 d], [1 e], [1 i], [1 k]): conical or tubulo-conical; smooth or moderately ribbed longitudinally; colours varying from purplish-pink to blackish-purple; often in obscure longitudinal stripes; orifice of shell rounded-trigonal.

Var. (2) vesiculosus (young) (Pl. [2], fig. [1 h]): exterior surface of the scuta impressed with small square holes, arranged in two or more rows, radiating from the apex of the valve.

Var. (3) validus (Pl. [1], figs. [c], [f infra]): globulo-convex; coarsely ribbed, ribs flexuous; either smooth or rugged; pale chocolate purple or pink; shell extremely strong; orifice almost circular.

Var. (4) zebra (Pl. [1], fig. [g]): conical; rich chocolate purple with broad snow-white ribs; sheath bright chesnut colour; summits of alæ oblique; orifice almost circular.

Var. (5) crispatus (Schröter) (Pl. [1], fig. [h]): pale blueish or pinkish-purple, with irregular rough projections, or with short, sharp, needle-like points; scuta with their exterior surface either plain, or with radiating lines formed of hood-like projecting points.

Var. (6) spinosus (Gmelin) (Pl. [1], fig. [i]): globulo-conical or cylindrical; shell rather thin, with long, upcurved, nearly cylindrical, very sharp points; colours very pale; attached to other specimens, and to Lepas anatifera.

Var. (7) coccopoma (Pl. [1], fig. [d]; Pl. [2], fig. [1 f], [1 l], [1 o]): globulo-conical; orifice small, rounded; walls generally smooth, thick; intense rose-colour, sometimes most faintly striped longitudinally with varying shades of pink; radii tinged with purple; scutum sometimes as in var. communis, sometimes with its basi-tergal corner much cut off, with the adductor ridge prominent, the pit for the depressor muscle deep, and the articular ridge broad and hooked; tergum sometimes as in var. communis, sometimes with a broader spur, placed nearer to the basi-scutal corner of the valve.

Var. (8) concinnus (Pl. [1], fig. [e]; Pl. [2], fig. [1 g]): globulo-conical; walls finely ribbed; dull purple, tinged and freckled with white; scutum, with a broad, hooked, articular ridge, with an extremely sharp plate-like adductor ridge, and with a cavity, bordered by a plate, for the rostral depressor muscle; tergum as in var. 1.

Var. (9) intermedius: radii with their summits slightly oblique; parietes pale blueish purple, with narrow dark purplish-blue longitudinal lines; sheath with the internal surface of the rostrum and lateral compartments much darker colored than the internal surface of the carina and carino-lateral compartments; scuta and terga as in var. communis.