186 GASTROPODA. [Pectinibranchia. 



Whirls 8, flattened, subtabulated. Suture linear, deep. Aperture sub- 

 quadrate. Peristome entire, equal, slightly reflexed. 



Diameter, 2-5 mm. ; height, 10 mm. 



Type in the U.S. Nat. Museum, Washington. 



If fib. Nmv Zealand (U.S. Expl. Ex.). 



Remark. Like the foregoing, this species has not been found 

 again. 



Fam. LITORINID.E, Gray. 



Animal having the proboscis wide and short ; tentacles long, 

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

 anteriorly truncate. Intromittant organ well developed, behind the 

 right tentacle ; reproduction oviparous or ovoviviparous. Eadula 

 long and narrow, formula 2+1+1+1 + 2. Central tooth of variable 

 size, with a few short denticles ; lateral and marginal teeth in oblique 

 rows, the lateral tooth large, tricuspid, marginals arcuate and denti- 

 culate. 



Distribution. World-wide. 



KEY TO GENERA. 



A. Shell imperforate, solid ; outer marginals of radula with 3 



denticles . . . . . . . . . . LITORINA. 



B. Shell rimate, chitinous, fragile ; outer marginals of radula 



multidenticulate . . . . . . . . . . L^EVTLITORINA. 



Genus 1. LITORINA, Menke, 1828. 



Litorina, Menke, Syn. Meth. Moll.. 1828. Type : L. liltorea, L. Litorina, 

 Menke: Ad., G.R.M., i, 312; Fischer, Man. de Conch., 707; Tryon, 

 Man. Conch. (1), ix, 229; Conch. Icon., x. 



Animal having the foot obtuse behind, longitudinally divided, so 

 that in walking each side advances alternately ; there are no append- 

 ages. Intromittant organ flat and rugose. The lingual ribbon is very 

 long, with a large number (up to 600) of rows of teeth. 



Shell imperforate, turbinate. coloured ; aperture rounded, not 

 notched below, the outer lip not thickened ; columella flattened or 

 excavated ; operculum horny, paucispiral ; nucleus more or less ex- 

 centric. 



The species inhabit the sea, brackish or sometimes even fresh 

 water, and are mostly littoral, feeding on algae. They are in a great 

 measure amphibious, living on rocks and grasses, where they are 

 washed by the high tide; they will consequently withstand depriva- 

 tion of water for a period. 



Some of the species are the food of man in Europe, and they are 

 also extensively gathered for bait. The best-known species, L. Uttorea, 

 is very abundant <> ike coasts of northern Europe ; 1,900 tons of this 

 mollusc are sold annually in the London market, employing a thousand 



