ABSTRACT

The shell is steeply conical, slightly compressed, with the lower part having rounded, approximate, radiating ribs; these ribs seem to be more prominent in the fossil than in the recent specimens. Colour dull purplish-red. Orifice oval, small, and narrow. The basis is not deeply conical, and occasionally is even flat: in the crag specimens it is almost wholly embedded in the coral to which it is attached; but in recent specimens it is generally exserted. Externally the basis is furnished with ribs corresponding with those on the shell. The largest recent specimens which I have seen, from St Jago, was 0*22 o f an inch in basal diameter; but some few o f the British specimens are nearly as large, and one of the fossils from the coralline crag a very little larger.