MOLLUSCA — PELECYPODS 



233 



Teredo (Fig. loi). Jurassic to present. 



Shell much reduced, globular, with valves gaping at both 

 ends. Pedal muscles attached to a long, narrow plate beneath 

 the umbos. 



The animal lodges at the inner end of a long burrow which it 

 has formed in wood. This burrow is lined by a shelly tube, 

 secreted by and covering the long conjoined siphons of the ani- 

 mal which extend from between the valves out to the open end 

 of the burrow. The free extremities of these siphons are pro- 

 tected by two small, movable, calcareous plates, the palets. 



The food introduced with the water into the branchial siphon 

 consists of Infusoria and other minute organisms. The wood 

 eroded by the animal in the formation of its burrow is of no nutri- 



FiG. 101. — -The "ship-worm," the pelecypod, Teredo navalis Linne, from the coast 

 of Massachusetts. In life a tube of lime carbonate encases the animal from the 

 shell is.) to the collar (c). c, collar; p., palets; s., shell; /., siphons. (From 

 Verrill and Smith.) 



tive value to it. It passes with no chemical alteration through 

 the digestive canal and is expelled through the anal siphon as 

 a mass of extremely minute particles which still retain their 

 fibrous structure. 



Teredo navalis is abundant on American and European shores, 

 doing great damage to submerged timbers, such as piers, ships, 

 etc. At one time it seriously injured the piles in Holland. 

 Various methods of metal sheathing have, however, been found 



