The Periwinkles and Chink Shells 



in oblique rows cross the spaces intermediate between the keels, 

 and granulations cover the whole surface. The body whorl has 

 a double set of strong tubercles and a smaller row between these. 

 The simple aperture is ribbed inside and tinted with the pale 

 chestnut that stains and streaks the colourless exterior. Alti- 

 tude, 2h inches. 



Habitat. — Australia, Ceylon. 



The Prickly Littorina (T. muricata, Linn.) has a solid, 

 yellowish gray shell with rounded whorls a little flattened below 

 the sutures and beaded with sharp nodules along the spiral ribs. 

 The aperture is nearly smooth, and brownish. This creature has 

 lived a year in a cabinet, cheerfully taking up its aquatic life 

 again when released. Length, i inch. 



Habitat. — Bahamas, West Indies, Florida. 



T. nodulosus, Gmel., is smaller, i to § inch long, dull 

 olive green or brownish yellow, spirally double-keeled and beaded, 

 with aperture smooth and brown. This "worthless Littorina," 

 as Reeve calls it, has a world-wide distribution. 



Habitat. — NorthCarolina to West Indies, Ceylon, Philippines, 

 Australia. 



THE CHINK SHELLS 

 Genus LACUNA, Turton 



Shell thin, ovate, turbinate or round, covered with epidermis; 

 aperture half-moon shaped; columella with groove or chink 

 leading to umbilicus; lip sharp; operculum thin, spiral. 



The Atlantic Chink Shell (L. vincta, Turton) looks at first 

 glance like an elongated znd thin specimen of Littorina. The 

 spire is smooth, horn-coloured, or banded with brown on a purp- 

 lish ground. The distinctive generic feature is the deep columellar 

 groove. It lives upon seaweeds in sheltered coves, and is often 

 quite as well represented as the periwinkles in the debris of an 

 inshore wind. Length, ^ inch. 



Habitat. — Arctic seas to New Jersey. 



The Chink Shell (L. porreda, Cpr.) has a wide groove, 

 and the body whorl is much enlarged. The creature is found 

 on seaweed. It is about ^ inch in diameter. 



Habitat. — Vancouver Island to San Diego, Cal. 



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