484 MANUAL OF THE MOLLTTSCA. 



long, slender, diverging, anal shortest, orifices plain; foot 

 large, tongue-shaped, pointed ; palpi triangular, nearly as largo 

 as the gills; branchise unequal, triangular. JDistribution, 

 Norway, Britain, Mediterranean, Black Sea, India. The species 

 are few, and mostly boreal, ranging from the laminarian zone 

 to 180 fathoms. (Forbes.) They live buried in sand and mud, 

 but when confined are able to creep up the sides of the vessel 

 with their foot. (Bouchard.) Fossil, 6 species. Eocene — . 

 Britain, France. 



Scrohicularia, Schumacher. Synonyms, Trigonella (part), Costa 

 (not L.), Ligula (part), Mont. "Le Lavignon" (Reaumur), 

 Cuv. Listera, Turt. (not E. Brown). Lutricola, Bl. Mac- 

 tromya, D'Orbigny (not Ag.) Type, S. piperata (Belon), Gmelin, 

 PI. XXI., Fig. 14. (See p. 60.) Shell oval, compressed, thin-, 

 sub-equilateral ; ligament external, slight ; cartilage-pit 

 shallow, triangular ; hinge-teeth small, 1 or 2 in each valve, 

 laterals obsolete ; pallial sinus wide and deep. 



Animal with the mantle open, margins denticulated ; siphons 

 very long, slender, separate, orifices plain ; foot large, tongue- 

 shaped, compressed ; palpi very large, triangular, gills minutely 

 striated, the outer pair directed dorsally. Lives buried, verti- 

 cally, in the mud of tidal estuaries, five or six inches deep. 

 (Montagu.) The siphons can be extended to five or six times 

 the length of the shell. (Deshayes.) The animal has a 

 peppery taste, but is sometimes eaten on the coasts of the 

 Mediterranean. 



Distribution, 20 species. Norway, Britain, Mediterranean, 

 Senegal. 



Fossil, 4 species. Tertiary. Europe. 



Mesodesma, Deshayes. 



Etymology, meso, middle, desma, ligament. 



Sijnonynu, Eryx, Sw. (not Daud.). Paphia (part), Lamarck, 

 1799 (see p. 464, note). Erycina (part), Lamarck, 1818 (not 

 Lamarck, 1805, nor Fabr., 1808). " Donacille," Lamarck, 1812 

 (not characterised) 



Examples, M. glabratum, Pi. XXL, Fig. 15. M. donacium, 

 Fig. 16. 



Shell trigonal, thick, compressed, closed ; ligament internal, 

 in a deep central pit ; a minute anterior hinge-tooth, and 1 — 1 

 lateral teeth in each valve ; muscular scars deep ; pallial sinus 

 small. 



Animal with mantle- margins plain ; siphons short, thick, and 



