Qapers, Piddocks^ and Ship-worms i 5 3 



each valve ; in the left valve there is a double 

 cardinal just below the beak which fits into a cavity 

 of the opposite valve formed b}^ two lar^e diverging 

 cardinals. The ligament uniting the valves is 

 exceedingly short, and admits of con- 

 siderable movement of the ends with- 

 out opening the shell throughout. 

 With the valves in their ordinary 

 positions the shell gapes equally at 

 each end, but the arrangement of teeth 

 and ligament is such that the front of 

 the shell may be entirely closed by 

 more widely expanding the rear, or 

 the hinder gape may be nearly closed 

 by separating the fronts of the valves. 

 They burrow vertically into deep mud, 

 the siphons reaching up to the surface, 

 and the only evidence that Lutraria 

 lies perhaps a couple of feet below is 

 an occasional spurt of water from the 

 excurrent siphon. To dig them out 

 from this deep retreat is the only way 

 to obtain living examples; but as the 

 situations they frequent are usually 

 lowest of tide-marks, this is no easy 

 the people of Herm, one of the Channel Isles, contrive 

 to get a sufficient number to eat; they know them 

 under the name of " Clumps." • It is an open question 

 whether the two so-called species are not forms of 

 the same. 



The Common Otter-shell (L. elliiJtica) is elliptical 

 in shape, somewhat flattened, solid and heavy 

 without being very thick. Where the olive 



Oblong Otter-shell 

 (one-fourth nat. size) 



beyond the 

 matter. Yet 



