232 13 ALAN ID JD. 



Var. angustus (Gmelin) PI. 5, fig. 1 a: pale dull 'purple or white; 

 orifice small or of moderate size ; radii very narrow or moderately 

 wide, white or pale purple, with oblique summits. 



Var. Cranchii {Leach) PI. 5, fig. lb: corroded, covered with fine 

 longitudinal ridyes owing to the exposed, filled-up, parietal tubes; dark 

 dirty ash-colour, with a Huge of purple : radii not developed, or very 

 narrow with oblique summits; orifice small. 



Var. fistulosus (Poll) PI. 5, fig. 1 d: shell cylindrical, white or dull 

 purple; orifice of moderate size or small; basis deeply cup-formed. 



Var. mirabilis, PL 5, fig. lc: briyht purple ; radii white, very 

 broad, with their summits parallel to the basis ; orifice entire, large. 



Hab. — Southern shores of England; South Wales; Mediterranean; Western 

 Africa, southward to Loanda, in9°S. ; West Indies (?). Generally adhering to 

 rocks at a low tidal level ; in one case attached to the floating Lepas Hillii, 

 Mus. Jeffreys. 



This is a well-marked species, and in its essential cha- 

 racters does not vary much ; but owing to the shell being 

 almost as often white as purple, — to its being remarkably 

 subject to disintegration, — to its often becoming cylindrical, 

 — to the radii being either not at all, or slightly, or mode- 

 rately, or largely developed, and consequently to the orifice 

 of the shell varying^ in size, the general external appearance 

 of the different varieties is singularly diversified ; but when a 

 series of specimens is examined, it is easy to see how one 

 form passes into another. 



General Appearance. — Shell conical, with the orifice oval, unusually 

 small, being generally only from one third to half of the basal dia- 

 meter ; sometimes moderately large; in one single instance as wide as 

 the basis. Radii, often represented by mere lineal fissures, or they are 

 narrow, or sometimes moderately wide. Colour pale, dull purple, 

 sometimes lilac, often passing into a dead pure white : the same indi- 

 vidual will occasionally have one part of its shell white, and another 

 purple: the purple tint almost invariably is nearly uniform, or not in 

 stripes. The radii are generally white, when the whole shell is purple, 

 but sometimes they are pale purple : the sheath is apparently always 

 coloured of a fine claret-purple, with the triangular portion of the alas, 

 added during diametric growth, generally white, but sometimes purple. 

 The surface is quite smooth, but very often, especially on the shores of 

 England, whole groups of specimens (excepting the very young ones,) 

 have had the outer lamina of the parietes entirely corroded and 

 removed ; in this case the shell assumes a dirty, more or less dark, 

 ash-colour, feebly tinted with purple, and the whole surface, owing to 

 the exposure of the solidly filled-up parietal tubes, becomes finely 

 striated, or covered with very narrow, longitudinal ridges. When 

 specimens are crowded together they often become cylindrical, and 



