papers, Piddocks^ and Ship-worms 159 



exposed is sufficient to cause their sudden disappear- 

 ance. They burrow in the sands about extreme 

 low-water mark ; not vertically but diagonally. 

 When the sands are covered with water their shells 

 are at the surface with the siphons exposed, but 

 when the sea goes out they retire beneath the sand, 

 going to the depth of a foot or two. If dug up and 

 placed upon the surface they bury themselves with 

 the rapidity of a mole. They can also dart rapidly 

 through the water, apparently by ejecting water 

 through the siphons. In many places they are 

 considered excellent food, and for this purpose they 

 are caught ^vith a bent or barbed wire thrust through 

 the open valves. The shells sometimes show at the 

 hinder end that like Lutraria they have no means 

 of ejecting sand that gets between the mantle and 

 shell, so are compelled to cover it over with a coat 

 of shell - matter. The late Mr. D. Robertson of 

 Cumbrae relates a singular experience. On the 

 recess of a spring tide he found three examples of 

 this Razor, whose shells protruded above the sand to 

 the extent of an inch and a half, and the mollusks 

 were unable to pull them down lower. To each 

 shell w^as attached several mussels who had attached 

 their byssus threads before the Razors realised what 

 it meant; but when the extra-low tide came these 

 tightly-moored mussels effectually prevented the 

 withdrawal of the Razors. 



The Sword Razor (S. ensis) in most respects 

 agrees with the Pod Razor, except that the shell is 

 curved as shown in the figure, and it never attains 

 the dimensions of the former species — 4 inches 

 being about its maximum length. It is more slender 

 II 



