370 LITTORINID.E. 



Var. 4. sinistrorsa. Spire of the shell turned to the left ; 

 that of the operculum dextrorsal or regular. 



Monstr. Keeled as in L. rudis the body-whorl furrowed, or 

 irregularly puckered lengthwise below the suture the spire 

 much elongated a new mouth thrown out or formed at the 

 side, and twisted backwards or distorted in other ways. 



HABITAT : Among stones and Fuel, and on rocks, be- 

 low high-water mark of neap tides ; extremely common. 

 The 1st variety frequents mud-flats in estuaries and tidal 

 inlets of the sea ; the 2nd was found by me on Llan- 

 rhidian salt-marsh near Swansea, at Southend, and in 

 Christiania fiord ; the 3rd occurred rather plentifully to 

 Mr. Barlee and myself in Loch Carron, and I have 

 solitary examples from other places ; of the 4th I pro- 

 cured two specimens at Billingsgate, and Mr. Rich ob- 

 tained a third which is now in Mr. Leckenby's collec- 

 tion. It is rather surprising that, considering the 

 enormous number of periwinkles brought every year to 

 this market, the reversed kind should be so excessively 

 rare. I was assured by all the dealers in shell-fish that 

 only these three specimens had ever been heard of. 3 

 and 4 are perhaps monstrous rather than varietal 

 forms. The distortions above noticed are found now 

 and then with the ordinary sort. Mr. S. Wood has 

 figured many of these monsters in his ' Monograph of 

 the Crag Mollusca.' L. litorea finds a place in almost 

 every list of our upper tertiary fossils, from Moel Try- 

 faen to the Red Crag; Sars has recorded it from the 

 Christiania district, in both older and newer deposits, 

 at heights varying from 100 to 460 feet ; and I observed 

 it at Uddevalla. The limits of its extra-British distri- 

 bution are comprised within Greenland (Morch) , White 

 Sea (Baer and Middendorff), and Lisbon (M f Andrew); 

 and Stimpson gives it as a New England shell. The 



