TEREDO. 



TESTA orbicularis, aequivalvis, inaequilateralis, 

 utraque extremitate hians, (hiatu antico postic?; 

 angulato, altero aiftice rotundato) antic^ suba- 

 lata, impressione musculari antica alae imposita; 

 dente elongato, sub umbone intern^ recurvo : 

 tubo postico, accessorio, longissimo, calcareo, 

 antice rariiis clauso, plerumque apertura ro- 

 tunda, postic^ in tubos duos diviso, operculis 

 duobus palmatisy aliquando pennatis instructo. 



In our last number we considered ourselves obliged to 

 establish three new Genera, at the same time expunging 

 one of those formerly published by Lamarck, so that in 

 reality we only added two to the Lamarckian list. In the 

 26th number we expressed our opinion that Lamarck's 

 Fistulana gregata might be added to his Genus Teredma, 

 upon a more careful examination we are now disposed to 

 abandon that opinion, and to unite Lamarck's Septariuy 

 together with his Fistulana gregata, with Teredo, thereby 

 lessening the number of genera by one because we 

 do not think there exist any characters by which they 

 can be distinguished ; which we will endeavour to show 

 by a recapitulation of the characters in which Lamarck 

 makes their distinctions to consist, together with our rea- 

 sons for regarding them as inconclusive. Teredo, accord- 

 ing to Lamarck, has a flexuous, cylindrical, shelly tube, 

 open at both endSj distinct from the shell, and covering 

 the animal ; and its shell consists of two valves, placed 

 without the tube at the posterior extremity. The charac- 

 ter of Lamarck's Septaria are, a very long shelly tube, 

 gradually attenuated towards the anterior (which should 

 be posterior) part, and divided interiorly by several. 



