26 CONCHOLOGY. 



Sumatra. It is the largest species known, some having 

 been seen four or five feet long. 



Shell thick, solid, very short or annular, open at both ex- 

 tremities ; equivalve, equilateral, angular and sharp ante- 

 riorly, only slightly touching by the opposite edges ; hinge 

 obsolete ; a considerable internal spoonlike cavity ; one 

 slightly sensible muscular impression. 



Tube more or less distinct from the substance in vi^hich 

 the animal lives, cylindrical, straight or flexuous, closed v\rith 

 age at the oral extremity so as to envelop the animal and its 

 shell ; always open at the other end, and divided interiorly 

 into two syphons by a middle partition. 



Teredo navalis. Teredo palmulata. 



T. gigantea. 



T. navalis. The common Ship Worm. 

 Species very thin, cylindrical, and smooth ; slightly twist- 

 ed, white, finely striated longitudinally. 



FAMILY II. 



Pholadaria. Two genera. 

 1, Pholas. The Stone Piercer. Nine species. 



This genus is without any tubular sheath ; it derives its 

 name from the Greek word ^wAew, to hide, alluding to the 

 custom of its inhabitant in forming cells in rocks, wood, &c. 



In form the Pholas is generally oblong, having two large 

 valves opposite to each other, with a number of smaller ones 

 attached to the back as a substitute for a hinge. The two 

 large valves never shut close ; they are open at one end, and 

 sometimes at both. 



The exterior of the shell is usually of a pure or dusky 

 white, but sometimes of a brownish cast. In some species 

 the shell is adorned with beautiful delicate reticulations, like 

 the finest lace ; in others the texture is coarser, like small 

 basket-work. They are found in the American, Indian, and 

 European seas, each shell in a separate habitation formed in 



