134 



Shell Life 



become naturalised in the Humber, where it was first 

 observed in 1864, from wliich. date it appears to have 

 gone on increasing in numbers. As it is an edible 

 species highly appreciated in the United States its 

 continued increase will probably bring joy to local 

 epicures. It may be noted that the word " niercen- 

 aria" refers to the former use of these shells in 

 making " wampum " — the strings of beads which 

 passed as money among the North American tribes. 



The Wavy Venus (Lucinopsis undata) is very like 

 the Round Double-tooth (Diplodonta) described in 

 the previous chapter, but whereas 

 that is a strong, glassy- white shell, 

 this is chalky-white and fragile. 

 It differs from the other Venus- 

 shells in being thin and almost 

 transparent. It is almost circular 

 in outline, swollen and smooth, 

 without ribs, but marked by 

 sunken concentric lines. Its colour 

 is white tinged with yellow near 

 the beaks. The impression of the 

 mantle within is very broad, and 

 the sinus extends far up towards 

 the beaks. The mantle-margin is wa\'y or uneven, 

 but neither fringed nor toothed. The orange siphons 

 are widely separate, protruding from the lower rather 

 than the hinder margin, and the lower tube is longer 

 than the upper, while both are fringed. It is a 

 common species everywhere in fine sand, even when 

 mixed with mud, and ranges between 3 and 100 

 fathoms. Full - grown specimens measure 1^ to 

 li inch in diameter. 



Warty Venus- 

 exterior and interior 



