HYDROBIA. 53 



lips are continuous aud make a complete peristome : operculum 

 horny and thin, marked with flexuous and rather strong lines 

 of growth, and having a small lateral spire of three whorls. 

 L. 0-25. B. 0-125. 



Yar. 1. albida. Of a whitish colour. 



Yar. 2. Barleei. Smaller and spindle-shaped, the last whorl 

 being contracted at the base, and the mouth much smaller 

 than usual. Rissoa Barleei, Jeffr. in Ann. & Mag. N. H. xix. 

 p. 310. 



Yar. 3. octona. Smaller, thin, glossy, and horncolour, with 

 the whorls more slowly increasing and divided by a deeper 

 suture. Helix octona, Linn. S. N. p. 1248. 



Habitat : All our tidal rivers, inlets, and bays ; cover- 

 ing mud-flats and oozy sands in countless profusion. 

 Var. 1 is occasionally found. Var. 2. Hebrides (Barlee 

 and J. Gr. J.) ; the typical form occurs in Loch Carron 

 and at Stornoway. This variety is littoral — although 

 the specimens (dead ones) which I described as Rissoa 

 Barleei were dredged in deep water, having accidentally 

 got there. Lindstrom noticed the same variety on the 

 eastern shores of the Baltic. Var. 3. In a large pool 

 of brackish water, called Arnold's Pond, near Grand 

 Havre Bay, Guernsey. This last variety inhabits the 

 southern shores of the Baltic; and M. Tasle sent me 

 specimens from Brittany. It may be a distinct species ; 

 but we do not know the effect of local conditions and 

 consequent change of food on the shape of animals. 

 H. ulvce is fossil in a post-tertiary deposit at Belfast 

 (Grainger) , Clyde beds (Smith and Crosskey) , Norwich 

 Crag (Woodward), Red and Coralline Crag (S. Wood), 

 Uddevalla (J. G. J.), Norway, in post-glacial beds (with 

 the variety Barleei) , from the present level of the sea to 

 130 feet above it (Sars). Its foreign range extends 

 from Finmark to Spain and throughout the Mediter- 

 ranean ; and Dr. Philip Carpenter has recorded it as a 



