484 “MANUAL OF THE MOLLUSCA. 
long, slender, diverging, anal shortest, orifices plain; foot 
large, tongue-shaped, pointed; palpi triangular, nearly as large 
as the gills; branchiz unequal, triangular. Distribution, 
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. Hocene—. 
Britain, France. 
Scrobicularia, Schumacher. Synonyms, Trigonella (part), Costa 
(not L.), Ligula (part), Mont. ‘‘Le Lavignon” (Reaumur), 
~Cuy. Listera, Turt. (not R. Brown). Lutricola, Bl. Mac- 
tromya, D’Orbigny (not Ag.) Type, 8. piperata (Belon), Gmelin, 
Pl. 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 im each yalve, 
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 mimutely 
striated, the outer pair directed dorsally. Lives buried, yerti- 
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. 
Synonyms, 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, Pl. XXI., 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 
