FAMILY 1. TUBICOLA. 37 



tulo ; tubo testaceo superne attenuato, aperto, apertura bilobata ; 

 interne in clavam ovatam, clausara, terminura habente. 



The genus Gastrochaena has been removed from the Pholadaria to the 

 Tubicola, because, like the rest of this family, the animal lines with a tes- 

 taceous tube the cavity in which it dwells ; it also forms an unconnected 

 tube for protection, when not imbedded. Its shell is equivalve, inequi- 

 lateral, gaping very widely on the anterior side in the form of an oblong 

 oval, united by a ligament behind, and having in the interior a small 

 spoon-shaped curvature ; a character which becomes more fully deve- 

 loped in the shells of Teredo and Pholas. 



The tube differs from that of Fistulana in being nearly divided into 

 two, at the upper end, by a kind of septum ; as also in its mode of habi- 

 tation, being often found in the open parts of dead shells, in which case 

 it forms a complete testaceous covering entirely foreign to its place of 

 attachment. 



Examples. 

 PL XX. Fig. 1 and 2. 



Gastroch.ena modiolina, Lamarck, Anim. sans vert., new edit., vol. vi. 



p. 49. 

 Fistulana modiolina, Deshayes. 

 My a dubia, Pennant. 



PI. XX. Fig. 3 to 5. 



Gastroch/Ena cuneiformis, Lamarck, Anim. sans vert., new edit., vol. vi. 



p. 49. 

 Fistulana cuneiformis, Deshayes. 

 Pholas hians, Chemnitz. 



TEREDO, Linnaeus. 



Testa orbicularis, insequilateralis, ad utrumque latus hians, dente elon- 

 gate, recurvo, infra marginem umbonalem utriusque valva? promi- 



