CONCHIFERA. 313 



low, 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, vertically, in the mud of tidal estuaries, 5 or 6 inches deep. 

 (Montagu.} The siphons can be extended to 5 or 6 times the length of the 

 shell. (Deshayes}. The animal has a peppery taste, but is sometimes eaten 

 on the coasts of the Mediterranean. Distr. Norway, Brit. Medit. Senegal. 

 Fossil, Pliocene, Brit. 



MESODESMA, Deshayes. 



Et-ym. Meso- middle, desma ligament. Syn. Eryx, Sw. (not Baud.) 

 Paphia (part) Lam. 1799 (see p. 299, note). Erycina (part) Lam. 1818 (not 

 Lam. 1805, nor Fabr. 1808). "Donacille," Lam. 1812 (not characterized). 



Examples, M. glabratum, PI. XXI. fig. 15. M. donachnn. fig. 16. 



SJiell trigonal, thick, compressed, closed; ligament internal, in a deep 

 central pit; a minute anterior hinge-tooth, and 11 lateral teeth in each 

 valve ; muscular scars deep , pallial sinus small. 



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

 orifices cirrated, branchial cirri dendritic ; foot compressed, broadly lanceo- 

 late : gills large, unequal ; palpi small. 



Sul-genus. Anapa, Gray. A. Smithii, PL XXI. fig. 17. Umbones 

 anterior, siphonal inflection obsolete. 



Distr. 20 sp. W. Indies, Medit. Crimea, India, New Zealand, Chili ; 

 sands at low-water. 



Fossil, 7 sp. Neocomian . U. S. Europe (Donacilla, D'Orb.) 



ERVILIA, Turton. Lentil-shell. 



Et.ym. Ervilia, diminutive of ervttm, the bitter- vetch. 



Type, E. nitens, P. XXI. fig. 18. 



Shell minute, oval, close ; cartilage in a central pit ; right valve with a 

 single prominent tooth in front and an obscure tooth behind ; left valve with 

 2 obscure teeth ; no lateral teeth ; pallial sinus deep. 



Distr. "VV. Indies, Brit. Canaries, Medit. Red Sea. 50 fms. 



DONAX, L. Wedge- shell. 



Ex. D. denticulatus, PL XXI. fig. 19. Etym. Donax, a sea-fish, Pliny. 



Syn. Chione. Scop. Cuneus, Da Costa. Capisterium, Meusch.* Latona 

 and Hecuba, Schuin. Egeria, Lea (not Roissy). 



Shell trigonal, wedge-like, closed; front produced, rounded; posterior 

 side short, straight ; margins usually creuulated ; hinge-teeth 2.2 ; laterals 



* Meuschen was a Dutch auctioneer; the names occur in his " sale catalogues." 

 Idivtte imposuere nomina absurda. Linnaeus. 



