NUCULA. 



545 



United States, Norway, the Cape, Japan, Sitka, and Chili. 

 They are usually from deep water, ranging from ten to one 

 hundred fathoms. There' are very numerous extinct species 

 from the Trias of Europe, India, and America. The 

 Nuculas differ from the Arks in the form of the gills, the 

 great development of the lahial tentacles, the absence of a 

 byssus, and the pearly nature of the shell. Dr. Carpenter 

 remarks that the inner layer of the shell exhibits a truly 

 nacreous structure, and that in the outer a small amount of 

 tubular structure may be observed. 



Species of Nucula. 



Bellotii, A. Adams. 

 castanea, A. Adams. 

 convexa, Sow. 

 crenulata, A. Adams. 

 Cuiningii, Hinds. 

 declivis, Hinds. 

 decussata, Sow. 

 delpliinodonta, Migh. 

 exigua, Sow. 

 gibba, A. Adams. 

 Japonica, A. Adams. 

 Layardii; A. Adams. 

 lucida, Gould. 

 margaritacea, A. Adams. 

 inarinorea, Hinds. 

 mitralis, Hinds. 

 nana, Hinds. 



nitida, Sow. 

 nitidula, A. Adams. 

 obliqua, Lam. 

 paulula, A. Adams. 

 Paytensis, A. Adams. 

 pisurn, Soiv. 

 Polii, Phil. 

 proxima, Say. 

 pulchra, Hinds. 

 radiata, Hanley. 

 rugulosa, Sow. 

 simplex, A. Adams. 

 Strangei, A. Adams. 

 striolata, A. Adams. 

 sulcata, A. Adams. 

 tenuis, Mont. 

 tumida, Hinds. 



Sub-geu. acila, H. and A. Adams. 



Shell with the surface of the valves divaricately sculptured. 



castrensis, Hinds. mirabilis, Adams and Ileeve. 



divaricate, Hinds. 



