LITTORINID^E. 229 



FAMILY LITTORINID^. 



Animal (PL 40, fig. 74.) Proboscis wide and short; tentacles 

 long, cylindrical, with eyes on small swellings at their outer bases; 

 foot anteriorily truncate. Penis well developed, behind the right 

 tentacle ; reproduction oviparous or ovoviviparous. Radula long 

 and narrow, 2-M-1-2 (PL 40, fig. 66.) 



Shell spiral, turbinate or globular, not nacreous; aperture oval- 

 rounded, entire, lip simple, coluinella thickened, flattened. Oper- 

 culimi (PL 40, fig. 75) corneous, paucispiraL The Littorinidse have 

 been monographed by Reeve, in Conchologia Iconica, vol. x, and by 

 Kiister and Weinkauff, in the Conchylien Cabinet. 



Synopsis of Genera. 

 Genus LITTORINA, Fer. 1821. 



Shell imperforate, turbinate, usually thick ; aperture rounded, 

 outer lip acute, coluinella rather flattened. 



Foot obtuse behind, longitudinally divided, so that in walking 

 each side advances alternately. The species inhabit the sea, brack- 

 ish, or sometimes even fresh water, and are mostly littoral, feeding 

 on alga3. Some of the species are the food of man in Europe, and 

 they are also extensively gathered for bait. The lingual ribbon of 

 the periwinkle is two or three times the length of the body of the 

 animal ; its canal passes from the back of the mouth under the 

 oesophagus for a short distance, then turns up on the right side, and 

 terminates in a coil resting on the plaited portion of the gullet; it 

 contains about 600 rows of teeth. 



The best-known species, L. littorea, is very abundant on the 

 coasts of Northern Europe, and is also rapidly extending its area 

 on our New England shores, where it appears to have been re- 

 cently introduced. 1900 tons of this mollusk are sold annually in 

 the London market, employing a thousand persons in gathering it. 

 It is extensively distributed by English fishermen over the oyster 

 beds, in order to keep them clear of sea-weed. 



This and other large species are in a great measure amphibious, 

 living on rocks and grasses where they are washed by the high 

 tide : they will consequently withstand deprivation of water for a 

 period ; and several specimens of a West Indian species existed for 

 over a year in my cabinet. 



About 150 species have been generally admitted, inhabiting all 

 parts of the globe. Fossil, they are rather numerous, commencing 



