la POPULAR BRITISH CONCHOLOGY. 



and many other mollusca^ speaks of rows of very minute 

 teeth or rasp-like processes on the valves, and supposes the 

 hollowing out to be caused by the motion of the valves in 

 the hole rasping against its sides. "We cannot however 

 discover these rasping points in the shells, but only crossed 

 strige. On the whole, the evidence of the Teredo is against 

 the rasping theory ; but of this we must speak again when 

 the character of Teredo comes before us. 

 The British species of Vholas are : — 



1. T. Norvegica : valves nearly as broad as long; pellets 



paddle-shaped. Plate II. fig. 6. 



2. T. navalis: valves extended laterally by auricles; pellets 



paddle-shaped, forked at the base. Plate II. fig. 3, 4. 



3. T. Megotara : valves distinguished by very wide and ho- 



rizontally spread auricles ; pellets spade-shaped. 



4. T. Upennata: valves with wide auricles; pellets long, 



pen-like. Plate II. fig. 5. 



5. T. malleolus: valves narrow; pellets shelly, mallet- 



shaped. 



6. T.pahnulata: valves like those oi itavalis ; pellets short, 



plumose. 

 The Teredo Norvegica^ imported from the North, and 

 naturalized among us, notwithstanding the partly success- 



