46 PHOLADARIA. 



you perceive, to a very different order. Clava- 

 fjella was till lately considered as existing only 

 in a fossil state. The researches of recent tra- 

 vellers have discovered Clavagella at Port Jack- 

 son, in Australia.* There is a specimen in the 

 British Museum. The valves are enclosed in the 

 tube. 



" The valves of Teredo are noticed as form- 

 ing part of the Linnsean generic character, you 

 will recollect. Lamarck considers them as true 

 Conchifera. In many specimens of Teredo the 

 valves are wanting, and the tube only remains. 



" The family Pholadarla contains, 



Pholas Pholas, stone-piercer. 



Gastrochoena Pholas and My a. 



" Notwithstanding the accessory pieces of the 

 hinge, Pholas is placed among bivalve shells, 

 the essential character of which is to have two 

 valves united by a hinge. The Pholas has a 

 foot or strong muscle, very thick and short. In 

 the next genus, composed of Pholas Mans and 

 Mya dnbia there are no secondary valves. 



" Allied to this family is Xylophaga dor salts, a 

 curious shell. One specimen has been lately found 

 at Gravesend, upon a stick. 



* See Penny Cyclopaedia, article Clavagella. 



