368 LITTORINID &. 
duced into large, long, arcuated, pointed auricles; posteally it 
becomes divided into two long, distinct tails or streamers, 
nearly coextensive with the shell in its axial admeasurement ; 
close to the bifurcation is a small opercular lobe without a 
caudal cirrhus, on which is fixed a beautiful white horny sub- 
oval operculum of 4-5 spires; the first two or three are small 
and concentrated, the last suddenly enlarges and closes the 
aperture, and is marked with delicate oblique striz of growth. 
The neck, when greatly protruded, is blotched at the sides 
and on the top with a claret-coloured red: these marks, and 
the eyes also, when not exserted, are conspicuous through the 
tenuity of the shell. 
This rare animal, of which I have taken seven live examples, 
dwells in a muddy-bottomed shelly district of the coralline 
zone in Exmouth Bay, eight miles from shore, in 15 fathoms 
water. 
This species has occasioned much difference of opmion; some 
naturalists have thought it distinct; others have considered it 
the Montaguan R. vitrea in a perfect condition, and looked on 
his shell as a specimen denuded of its striz by attrition. They 
say that many of the so-called R. vitrea of the cabimets, when 
placed under the microscope, exhibit traces of the striz of 
the ‘proxima’: in this fact they are probably correct, because 
these smooth examples may really be that species; but they 
are wrong in their conclusions that it is Montaguw’s shell, as 
will appear by the discovery of a perfect specimen and lively 
animal of a species, which, I think, whatever doubts may still 
exist, must now be considered the “smooth shell” of that 
author, long known as the Turbo vitreus, and which has not 
the slightest traces of spiral strie. The present difficulty has 
arisen from Montagu’s description suiting a worn ‘ proxima,’ 
or the shell I propose to regard as the ‘vitrea” If I had 
not made the present capture, I should, lke others, have 
judged the two to be different conditions of the same species ; 
but I think it will appear, from what will be subsequently 
stated, that even the shells of the ‘proxvima’ and ‘vitrea’ 
exhibit a slight but constant variation, and that the animals 
are very distinct. 
2 
