378 LITTOEINID.E. 



Rissote without that appendage ; indeed, if we were to look for 

 strict typical specialties in either the hard or soft parts of any 

 mollusk, every species must become a genus. 



Shell. Of eight yellowish-white, rounded, finely reticu- 

 lated volutions with oblique well-marked sutural lines. The 

 apex is obtuse and not reflexed, as stated by me in another 

 place: I was deceived by imperfect specimens, which led 

 me into the error of supposing that it would prove a 

 Chemnitzia. 



This is one of the slenderest British shells, having only an 

 axial admeasurement of -jV, and a diameter of ^V uricise the 

 outer lip is thin, and the aperture is oblong-oval and almost 

 entire. 



Animal. The general colour is hyaline- white, shot through- 

 out all its organs with a mixture of very minute close-set 

 points, short lines or blotches, of flaky and frosted snow- 

 colour. Mantle even with the shell, except that at the aper- 

 tural upper angle it emits the filament I have so often men- 

 tioned as being present in all the Rissoa, and whose particular 

 function is doubtful. The muzzle is slender and rather long, 

 having the first half from the neck, on its upper part, clothed 

 with a very close tunic or tight overlay ; the disk is smooth, 

 compressed, bevelled to a fine edge, and almost circular, with 

 a median vertical fissure on the under surface, in which I have 

 often seen the delicate white corneous plates, jaws, and lingual 

 riband ; but great powers and much time are required to seize 

 a favourable opportunity of vision in so minute and restless a 

 being. The tentacula are very like those of Rissoa striata, 

 moderately long, flat, rounded or obtuse at the tips, quite 

 smooth even under .high powers, divergent, with large black 

 eyes, not on pedicles or prominences, but fixed on the centre 

 of their bases with very little external inclination, and widely 

 apart; there is no connecting tentacular veil, nor the least 

 triangularity, foldings, or the presence of apical inflations, as 

 in the Chemnitzia ; on the march the eyes are usually carried 

 within the margin of the shell. The foot is slender, greatly 

 hollowed out in front and deeply labiated, with distinct, long, 

 arcuated linear auricles which play on the march, or, as 



