The Mussels and Rock-eateis 



dorsal line short; beaks minute, incurved; epidermis thick, 

 dark ; lining pearly. When young, these mussels are suspended 

 to rocks by the byssus. At maturity they bore into limestone 

 rock and cannot turn around. The calcareous shell of Spondy- 

 lus is often burrowed, especially of the ponderous species. The 

 shell is often thickened by a limy deposit. The animal is luminous. 



A small genus of forty species, well represented in the West 

 Indies. 



The Rock-eater (L. Uthophagus, Linn.) is shaped like a 

 pea pod, and has a smooth, chestnut exterior. It is found in 

 coral rocks. Length, 2 to 3 inches. 



Habitat. — Europe, West Indies, Florida Keys. 



Genus LITHOPHAGUS, Muhlf. 



The Plumed Rock-eater (L. -plumula) Hanley, is very like 

 the last. It burrows in rocks and old shells. Length, i to 2 

 inches. 



The Mediterranean L. dactylus is highly esteemed as food. 



Genus ADULA, H. & A. Ads, 



The Pea Pod Shell {A. falcata, Gld.) is described by its 

 name. The shell is thin and of the texture of rubber, white and 

 pearly within, with a wrinkled brown epidermis. It is able to 

 bore into very hard rock, forming a burrow to the sides of 

 which it fastens itself by the byssus. Length, 2 to 3 inches. 



Habitat. — California coast. 



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