COSVHYLlk—DITHYRA. 2. 1,3 



2. TEREDO— LINN]E. 



Testa orbicularis, hemisphcBi'ica, ^equivalvis, tuho lougo cylin- 

 draceo cum acvessoriis variis postice terminata. Cardo dente 

 longo curco sub marginem inserto, in utrdque valvd : lateral 

 libtis nullis. Ligamentuin nullum. 



SUell orbicular, hemispherical, equivalve, terminating behind in a 

 long cylindrical tube with its various appendages. Hinge with 

 a long; curved tooth in each valve, inserted under the margin : 

 lateral teeth none. Ligament none. 



Besides the long cylindrical tube, which is gradually formed 

 for protection in the passage of the animal through the wood, the 

 valves of this genus may be distinguished from those of the 

 Pholas by the triangular projection at the anterior end of each. 

 They are all inhabitants of the ocean, ministers of the decompo- 

 sition and destruction of timber, the calamity of ships and driven 

 piles. 



Linne, and tlie subsequent writers on systematic concholoo-y, 

 have formed the characters of this genus from the cylindrical 

 tube. Lamarck has made his specific characters from the dif- 

 ferences of tlie appendages placed near the smaller end of the 

 tube. In conformity, however, with the other bivalves, we consi- 

 der the primary valves as offering the most decided and natural 

 basis of specific distinction. 



Lamarck has also placed this genus and that of the Pholas in 

 his division with the ligament external. They have, however, no 

 permanent ligament, as we observed of the Pholas tribe, but the 

 valves are merely connected together by a fold of the animal 



