78 NATURAL HISTORY. 



seen, and how it is effected by the respiratory process. 

 The Barnacle or Duck Shell resembles the above, but 

 is larger, and has a more fragile shell, which is, as is 

 well known, used by painters. 



The River Pearl Shell (mya margaritifera) is black 

 on the outside ; the interior of the shell is lined with 

 thick laminae of beautiful mother-of-pearl ; its length is 

 about four inches, its breadth two; pearls are found 

 within the valves, but much inferior in beauty to the 

 Oriental. They are found in the Elbe, the Moldau, 

 and other streams in Middle Germany. 



The Tellina, Tunkenshell (tellina gari) is oval, two 

 inches long and one broad; gray, rayed with brown. 

 The flesh is white and soft, and the liver being first re- 

 moved, pickled with vinegar and spices, is much esteemed 

 as sauce. It is met with in all the southern seas, but 

 principally in the Mediterranean. 



The Razor Shells, Knife Handles (solen vagina), so 

 called from their elongated form resembling the handle 

 of a dessert knife, are six inches long, of a green color, 

 striped with red. They are found on the coasts of Europe, 

 but principally on those bordering on the Mediterranean, 

 where they are very numerous. 



The Stone Finger (pholas dactylus) is over three 

 inches in length, one in thickness, and is striated in a 

 kind of network. The shell is very easily broken, never- 

 theless, they can excavate tubes or long cells in the hard- 

 est wood or even lava, like the Mytilas. The flesh is 

 considered superior to the oyster in flavor and tender- 

 ness. 



The Ship Worm (teredo navalis) has no proper shell, 

 but is an almost vermiform body, about half a foot in 

 length, about as thick as a grub worm, and is celebrated 



