With respect to _var. intermedius_ I have little to say in addition to the character given above: I have seen only two groups of specimens in Mr. Cuming's collection: the chief interest in this variety is that it shows that the next form must be ranked as a variety, and not as a distinct species. Of _var. occator_ (Pl. 1, fig. _k_) I have seen several specimens, mostly taken off the bottoms of vessels, and one specimen, marked in Mr. Cuming's collection "South Seas." After having carefully examined these specimens, I came to the conclusion, that the slightly oblique radii--the general colouring, and more especially that of the sheath--the scuta (Pl. 2, fig. 1 _b_), with their sharp hood-like points, in radiating lines--and the terga, with the spur so near to the basi-scutal angle, were amply sufficient to distinguish it as a good species. Subsequently, however, I found that the scuta in _var. crispatus_ presented, both externally and internally, exactly the same peculiar appearance. In _var. intermedius_, I found the summits of the radii equally oblique, and the general colouring nearly the same, and more especially a close approach to the singular circumstance of the sheath differing in colour towards the opposite ends of the shell. So that the position of the spur of the tergum was the chief remaining character; and this evidently varied considerably in the four or five specimens examined by me, being either its own width, or much less than its own width, from the basi-scutal angle: the outline, also, of the small portion of basal margin, between the spur and the basi-scutal angle, likewise varied much, being either angularly indented, or gradually curved down towards the spur: so also the tip of the spur varied in shape. The longitudinal furrow is unusually apt, in this variety, to remain open. We know that the position of the spur varies considerably in _var. communis_. Hence, although the spur, on an average, lies closer to the basi-scutal angle in this than in any other variety, even than in _var. d'Orbignii_, it would, I conceive, be preposterous to found a species on this one character. In the animal's body, every part agrees perfectly with that of _var. communis_.