248 NUCULID^. 



{Arcacea.) 



Family NFCULID^. 



Shell oval or trigonal, small, nacreous within ; hinge composed 

 of a great number of transverse teeth, interrupted b}^ a central 

 pit for the reception of the ligament, which is internal or external. 



NucuLA, Lam. 



Etym. — Diminutive of nux, a nut. 



Syn. — Polydonta, Muhlf. Nuculites (part), Conrad. 



Distr. — 50 sp. Northern and Arctic seas; 10-180 fathoms. 

 Siberia, Melville Island, New England, Britain, Mediterranean, 

 Cape, Japan, Australia. Fossil, 250 sp. (50 Palaeozoic, 30 Trias, 

 TO Cretaceous, 100 Tertiary.) United States, Europe, South 

 India. N. obliqua, Lam. (cxxvi, 21). 



Shell trigonal, with the umbones turned towards the short 

 posterior side ; smooth or sculptured, epidermis olive, interior 

 pearly margins crenulated ; hinge with prominent internal 

 cartilage-pit, and a series of sharp teeth on each side ; pallial 

 line simple. 



Animal with the mantle open, its margins plain ; foot large, 

 deeply fissured in front, forming when expanded a disk with 

 serrated margins ; mouth and lips minute, palpi very large, 

 rounded, strongly plaited inside and furnished with a long con- 

 voluted appendage ; gills small, plume-like, united behind the 

 foot to the branchial septum. 



The Nucula uses its foot for burrowing, and Professor Forbes 

 has seen it creep up the side of a glass of sea- water. The labial 

 appendages protrude from the shell at the same time with the 

 foot. 



ACiLA, H. and A. Adams, 1858. Valves divaricately sculptured. 

 3 recent species. N. divaricata^ Hinds (cxxvi, 28). Fossil. N. 

 ornatissima, d'Orb. (cxxvi, 29). Cretaceous. 



Leda, Schumacher, 1817. 



Etym. — Leda^ in Greek mythology, mother of Castor and 

 Pollux. 



Syn. — Lembulus (Leach), Risso. Nuculana.Link. Dacrj^omya, 

 Agass. Jupiteria, Bellardi. Junonia and Saturnia, Seguenza. 



Distr. — 80 sp. Northern and Arctic seas; 10-180 fathoms. 

 Siberia, Melville Island, New England, Britain, Mediterranean, 

 Cape, Japan, Australia, P'ossil, 190 sp. Silur. — ; United States, 

 Europe, South India. L. pernida., Miill. (cxxvi, 31 \ 



Shell resembling Nucula ; oblong, rounded in front, produced 

 and pointed behind ; margins even ; pallial line with a small 

 sinus ; umbonal area with a linear impression joining the anterior 

 adductor. 



