284 



LIFE BY THE SEASHORE. 



tilage internal placed in a deep pit, the teeth consist of two 



diverging cardinals in each valve and two rudimentary 



laterals. 



We come next to the razor-shells, or Solens, interesting 

 Bivalves which cannot be confused with 

 any others, and which are very common, 

 though not often seen in the living 

 state. They live near low-water mark, 

 where they burrow deeply in the sand, 

 but may be readily dug out by an expert 

 digger. We have two common species 

 Solen siliqua (see Fig. 82), the common 

 "razor-fish," in which the shell is almost 

 straight and the ends are both abruptly 

 truncated, and S. ensis, which is much 

 smaller, distinctly curved, and has the 

 anterior end more rounded than the 

 posterior. It is unnecessary to describe 

 the shell, for this must be familiar to 

 everyone ; but it should be noticed that, 

 like those of Mya and Lutraria, it gapes 

 widely at both ends. The shape of the 

 foot is interesting, and its efficiency as 

 a burrowing agent should be noted on 

 the shore; it will be noticed that its 

 general appearance varies much, accord- 

 ing as it is in action or at rest. It 

 protrudes from the anterior extremity 

 of the shell, and the united siphons 

 from the posterior. When the animal 

 is undisturbed these are protruded at 

 the surface, and have the usual func- 

 tions. 



The two last Bivalves we shall con- 



FIG. 82. Razor -shell sider make their homes not in sand or 

 (Solen siliqua). /.foot; mu( j k u t i n rocks, into which they 



at the other end the . , . ' . J 



siphons (s) are visible, burrow deeply. Ihese are Saxicava 



rugosa and the species of Pholas. The 



first is abundant everywhere, wherever suitable rocks 



occur. It is common in limestone, which is often literally 



honeycombed by its burrows. The blocks are thus ren- 



