LACUNA. 353 



Hebrides (Barlee). In a fossil state L. pallidula, var. 

 neritoidea, was found by me at Fort William ; and the 

 ordinary form is enumerated in Godwin- Austen's list of 

 shells from an upper tertiary deposit in Sussex. In a 

 recent state the latter has been recorded from the Bou- 

 lonnais (Bouchard-Chantereaux), Quiberon and Belle- 

 ile in Brittany (Tasle), and Loire-Inferieure (Cailliaud); 

 and the former ranges from Heligoland northward to 

 Iceland, Greenland, Spitzbergen, New England, and 

 Massachusetts. 



Mr. Clark says that the opercular lobe has occasion- 

 ally four caudal filaments. I never saw more than two 

 in the numerous specimens which I have examined of 

 the typical form and principal varieties. He also de- 

 scribes the tentacles as " setose." This character I 

 have likewise failed to detect, although I used the 

 same optical aids for observation that he did. The edges 

 of the tentacles are more or less uneven and sometimes 

 serrated, arising (as I believe) from the contractility of 

 these organs ; possibly such appearances may have mis- 

 led Mr. Clark, and induced him to consider them as in- 

 dicating hairs or setae. A specimen in my cabinet of 

 the variety neritoidea is distorted by having a rather 

 deep and irregular indentation down the front. The 

 fry of this variety are of a light horncolour ; the colour 

 of the animal in the adult state is greyish, with a faint 

 tinge of purple. Perhaps this may be a distinct species ; 

 but as I am not satisfied on this point, I prefer leaving 

 it to the judgment of my brother conchologists. To 

 add another species to the list of any local fauna or 

 flora, unless on conclusive grounds, would indeed be 

 unworthy of a naturalist. 



L. retusa of Brown appears to have been described and 

 figured from a half-grown shell of the present species. 



