37 



T. Gigantea, which sometimes exceeds four feet in 

 length, and several inches in circumference. 



Teredo navalis Teredo palmulatus. 



PHOLAS. 

 pholas. — Linnaeus. 

 This well known shell is described by La Marck as a 

 bivalve, but without any tubular sheath inclosing it, 

 though very similar in form to those which have. — It 

 has one or more accessory valves, either at the hinge or 

 above it. The inferior, or lower margin of the valves, 

 recurved outwardly. 



In this shell, the valves being sufficiently large to 

 protect the greater part of the animal, it does not re- 

 quire, as in the preceding genera, a sheath to defend 

 their very long bodies. The Pholas pierces stones, 

 chalk, and wood, from whence it cannot remove itself. 

 Pholas dactylus Pholas silicula 



orientalis costata 



Candida crispata 



dactyloides callosa 



Pholas clavata. 



