Nor have I any doubt that _var. crispatus_, of Schröter (Pl. 1, fig. _h_), is only a variety, although the scuta in some specimens have a peculiar appearance, externally like these valves in _var. occator_ (Pl. 2, fig. 1 _b_): the scutum is here broader and flatter than in _var. communis_, and the adductor ridge is very feebly developed, but we shall see how variable this ridge is in all the varieties: externally, the sharp, hood-like points formed by the upturned lines of growth, have a very remarkable appearance, from being arranged in quite straight radiating lines. This structure is evidently caused by the same tendency which produces on the walls the sharp, upturned, irregular points; but it is singular that the scuta are smooth in some specimens with very rough parietes; and, on the other hand, bristling with the symmetrically arranged, hood-like projections, in other specimens on which I could with difficulty detect only a few exceedingly minute points on the walls. In _var. communis_ I have seen a few specimens with a slight tendency in the scuta to become striated longitudinally. The tergum in _var. crispatus_ presents no difference from that in _var. communis_. Some of the roughest and best characterised specimens of _var. crispatus_ appear to have come off copper-sheathed vessels. I believe _var. spinosus_ of Gmelin (Pl. 1, fig. _i_), has been correctly considered by me as a variety, but I have unfortunately seen only one set of specimens with their opercular valves preserved: these were attached to _Lepas anatifera_. The colour of the shell varies from reddish-purple to nearly white; the radii are sometimes quite white; the walls are slightly ribbed. The scuta in the above specimens, externally were smooth; the adductor ridge was rather more distinct from the articular ridge than in any other variety; and the terga rather more plainly beaked. The tubular, up-curved, calcareous spines sometimes occur only on one side of the shell, and often only in the lower part. These spines are often coloured brighter than the walls. Their presence cannot be accounted for (any more than the state of the scuta in the foregoing _var. crispatus_) by the nature of the surface to which they are attached; for I have seen one set attached to a large rugged specimen of _B. tintinnabulum_, and another to the very smooth valves of _Lepas anatifera_. I believe that this form is almost always associated with _var. communis_, which is an argument that it is only a variety.