316 MANUAL OF THE MOLLUSCA. 



the pallial sinus. Animal with a long, truncated foot ; siphons separate, 

 diverging, fringed. Distr. 1 sp. Brit. Medit. Senegal, Red Sea. Fossil, 

 1 sp. Pliocene — . Italy. 



Machcera, Gould. (Siliqua, Megerle. Leguminaria, Schum.) M. polita, 

 V PI. XXII. fig. 7. Shell smooth, oblong; epidermis polished; umbonal rib 

 H^ extending across the interior of the valve ; pallial sinus short. The animal, 

 "^ figured liy MiddendorflF, is similar to Solecurtus. Distr. India, China, 

 Ochotsk, Oregon, Sitka, Behriug's Sea, Newfoundland. M. costata, Say, is 

 often obtained from the maw of the cod-fish. Fossil, 4 sp. U. Green- 

 sand — . Brit. France. 



Solecurtus, Blainville. 



Mi/m. Solen and curtiis, short. 



Syn. Psammosolen Eisso. Macha, Oken. Siliquaria, Schum. 



Ex. S. strigilatus, PI. XXII. fig. 8. S. Caribous, PI. XXII. fig. 9. 



Shell elongated, rather ventricose, with sub-central beaks ; margins sub- 

 parallel ; ends truncated, gaping ; ligament prominent ; hinge-teeth f ; pal- 

 lial sinus veiy deep, rounded ; posterior adductor rounded. 



Animal very large and thick, not entirely retractile within the shell ; 

 mantle closed below ; pedal orifice and foot large ; palpi triangular, narrow, 

 lamellated inside; gills long and narrow, outer much shortest; siphons 

 separate at the ends, united and forming a thick mass at their bases ; anal 

 orifices plain, branchial fringed. 



The Solecurti bury deeply in sand or mud, usually beyond low-water, and 

 are difiicult to obtain alive. P. Carihceiis occurs in couutless myriads in the 

 bars of American rivers, and on the coast of New Jersey in sand exposed at 

 low-water ; by removing 3 or 4 inches of sand its burrows may be dis- 

 covered; they are vertical cylindrical cavities, \\ inches in diameter and 12 

 or more deep, the animal holds fast by the expanded end of its foot. 



Distr. 25 sp. U. States, Brit. Medit. W. Africa, Madeira. 



Fossil, 30 sp. Neocomian — . U. S. Europe. 



Sub-genus, Novaculina, Benson. N. gangetica, PI. XXII. fig. 10. Shell, 

 oblong, plain ; epidermis thick and dull ; pallial sinus rather small ; anterior 

 pedal scar linear. Distr. India, China. In the mud of river-estuaries. 



FAMILY XVIII. Myacid^. 



Shellihick, strong and opaque ; gaping posteriorly; pallial line sinuated ; 

 epidermis wrinkled. Structure more or less distinctly cellular, with dark 

 nuclei near outer surface ; cartilage process composed of radiated cells. 



Animal with the mantle almost entirely closed ; pedal aperture and foot 

 small ; siphons united, partly or wholly retractile ; branchiae 2 on each side, 

 elongated. 



