Handbook of Paleontology 155 



can be expanded at the apex into an umbrella shape, and 

 through this expansion the clam swims backwards, hence 

 the name. It can swim a considerable distance. The 

 shell is three-quarters of an inch long, thin and flexible, 

 of a rich brown color with yellow lines radiating from 

 the hinge. It ranges from North Carolina to Nova Scotia. 

 The Angel's Wings which burrow in wood, rock or even 

 clay banks, elsewhere, burrow deep in sand along the 

 Florida coast. The shell of another borer will be found 

 washed up on sandy beaches. This is the Ship- Worm 

 {Teredo navalis). It is wormlike in form with a small 

 bivalve shell at the end, and it owes this form to its habit 

 of burrowing into any sort of wood except palmetto or 

 teak. This form is abundant along our shores and also 

 on the coasts of Europe. It has done great damage to 

 the dikes of Holland. There are many forms of these 

 boring mollusks in southern waters. They are exceed- 

 ingly destructive. Submerged timbers are burrowed and 

 soon rendered useless; also ships, piles of wharves, buoys 

 etc. come in for their attacks. In temperate waters these 

 borers sometimes attain a length of six inches, but in 

 tropical waters they have been found with a length of 

 ten feet. The Razor Clam (Ensis americana-Solen 

 ensis) is a common species upon the New England and 

 New Jersey coasts on sandy beaches or sandy bars where 

 the water is not brackish. It is found from Labrador to 

 the Florida Keys. It is very palatable, but is practically 

 impossible to capture as it burrows very rapidly into 

 sandy beaches when disturbed. The shell is about six 

 inches long and one inch wide, and there is a long mus- 

 cular foot through which the rapid burrowing is accom- 

 plished. The Razor Shell (Pinna muricata) is very 

 abundant in Florida waters, often found associated with 



