36 CLASS I. TROPIOPODA. ORDER I. BIMUSCULOSA. 



Example. 

 PI. XVIII. Fig. 1 to 4. 

 Clavagella aperta, Sowerby, Genera of Shells, No. 13. Deshayes, 

 Enc Me'th., vol. ii. p. 240. 



FISTULANA, Bruguiere. 



Testa aequivalvis, inaequilateralis, ad marginem basalem hiantissima, la- 

 tere antico brevissimo ; in parte inferiori tubi testacei inclusa ; tubo 

 interne clauso, superne perforato, attenuate 



In the genus Fistulana the bivalve shell is altogether free, and inde- 

 pendent of the tube in which it is confined ; and the lower end of the 

 tube is convexly closed over. Only two of Lamarck's species are refer- 

 able to this genus, his Fistulance clava and gregata ; the rest belong to 

 the genera Gastrochana and Teredo. 



The shell of Fistulana consists of two irregular, inequilateral valves, 

 gaping widely at the basal margin, and united by a soft ligament. It is 

 entirely free, inclosed in the lower expanded cavity of a long, straight, 

 clavate tube which it forms in the sand: the lower end is closed, the 

 upper end open. 



Example. 



PI. XIX. Fig. 1 to 5. 



Fistulana clava, Lamarck, Anim. sans vert., new edit., vol. vi. p. 30. 



Enc. Me'th., vol. ii. p. 140. pi. 167. f. 17 to 22. 

 Teredo clava, Gmelin. 



GASTROCH.ENA, Spengler. 



Testa aequivalvis, inaequilateralis, subcuneiformis, antice hiantissima ; 

 hiatu ovali, postice attenuato ; cardine lineari, marginali, subeden- 



