60 * THE PROCEEDINGS OF THE LINNEAN SOCIETY 



Littorina has been subdivided by different authors. There are 

 about 200 species at present known. But many of these will 

 need reduction. The following very complete and excellent 

 notice of the family is from Woodward's Manual of the Mollusca 

 (Tate's Edition). 



Family Littorindj;. 

 Shell turbinated or depressed, never pearly, aperture rounded, 

 peristome entire ; operculum horny, pauci-spiral ; animal with 

 a muzzle-shaped head and eyes sessile at the outer base of the 

 tentacles ; tongue long and armed with a medium series of broad 

 hooked teeth, and three oblong hooked uncini ; branchial plume 

 single ; foot with a linear duplication in front and a groove along 

 the sole ; mantle with a rudimentary siphonal canal ; operculum 

 lobe appendaged. The species inhabit the sea or brackish water 

 and are mostly littoral feeding on alg£e. 



Littorina, Ferussac. 

 Shell turbinated, thick, pointed, few whorled ; aperture rounded, 

 outer lip acute, columella rather flattened, imperforate ; operculum 

 pauci-spiral ; lingual teeth and trilobed uncini hooked and den- 

 tated ; 131 species. He adds. " the perry-winkles are found on 

 the seashore in all parts of the world ; in the Baltic they live 

 within the influence of fresh water and frequently become dis- 

 torted ; similar monstrosities are found in the Norwich Crag. The 

 common species (L. littorea), is oviparous ; it inhabits the lowest 

 zones of seaweed between tide marks. An allied species 

 (L. Tudis), frequents a higher region where it is scarcely reached 

 by the tide ; it is viviparous and the young have a hard shell 

 before their birth, in consequence of which the species is not 

 eaten. The tongue of the winkle is two inches long ; its foot is 

 divided by a longitudinal line, and in walking the sides advance 

 alternately. The perry-winkle and the trochus are the food of 

 the thrush in the Hebrides during the winter. The lingual canal 

 passes from the back of the mouth under the oesophagus for a 

 short distance, then turns up the right side and terminates in a 

 coil like spare rope resting on a plaited portion of the gullet. It 

 is 2^ inches long and contains about 600 rows of teeth, the part 



