260 Mr. W. Clark on some undescribed Animals 



The tentacula are flat, strong, rather short, flake-white, smooth, 

 gently attenuating and becoming minutely claviform at the tips, 

 which are each clothed with six comparatively long, intensely 

 aciculate setse ; the eyes are unusually large, black, and fixed on 

 minute demi-semicircular lateral excrescences at the external 

 bases, and are so amalgamated with them as scarcely to present ■ 

 a prominence. The foot is a curious organ, being large, fleshy, 

 anteriorly grooved, so as to form a slight labium, deeply indented 

 in the centre, and produced 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 ad- 

 measurement ; close to the bifurcation is a small opercular lobe 

 without a caudal cirrhus, on which is fixed a beautiful white 

 horny suboval operculum of 4-5 spires ; the two or three first are 

 small and concentrated, the last suddenly enlarges and closes 

 the aperture, and is marked with delicate oblique striae 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 a diff'erence of opinion ; some na- 

 turalists 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 striae by attrition ; they say that 

 many of the so-called R. vitrea of the cabinets, when placed under 

 the microscope, exhibit traces of the striae 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 conclu- 

 sions that it is Montagues 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 considei'ed 

 the " smooth shell " of that author, long known as the Turbo 

 vitreus, and which has not the slightest traces of spiral striae. 

 The present difiiculty has arisen from Montagues description 

 either suiting a worn ' proxima,' or the shell I propose to regard as 

 the ' vitrea.' If I had not made the present capture, I should, like 

 others, have judged the two to be diff'erent conditions of the 

 same species ; but in the next article I think it will appear that 

 even the shells of the ^proxima ' and ' vitrea ' exhibit a slight 

 but constant variation, and that the animals are very distinct. 



August 14. — I have just taken another lively example of this 

 species, and I need only remark, that the peculiar gait above 

 mentioned was less apparent than in the animal already de- 



