TEREDO. 171 



It is the T. navium of Sellius, T. navalis of Gmelin 

 and of almost every subsequent writer nntil Loven 

 identified that species with the T. marina of tlie first- 

 named author^ T. nigra of De Blainville, T. communis of 

 Osier, T. Brugiderii of Delle Chiaje, T. fat alls and T. 

 Deshaii of Quatrefages, and T. Senegalensis of Laurent 

 but not of De Blainville. The sheath appears to be the 

 Fistulana corniformis of Lamarck; and I suspect that, 

 in one of the earliest stages of growth, it is the Denta- 

 lium bifissum of S carles Wood fi'om the Coralline Crag, 

 the smaller opening of which exhibits the same internal 

 ridge or partition between the pallial tubes that is so 

 characteristic of this part of the sheath in T. Norvegica. 

 No Dentalium has any such process. 



2. T. nava'lis*, Linne. 



T. navalis, Linn. S. N. p. 1267 ; R & K. i. p. 74, pi. iv. f. 7, 8, and 

 xviii. f. 3, 4. 



Shell resembling that of T. Norvec/ica, except in being of a 

 much smaller size, and having a thinner texture and finer sculp- 

 ture; the posterior auricle in the present species is proportion- 

 ately larger, not placed so high up, more compressed, and better 

 defined both outside and inside (especially the latter) by means 

 of a thin overlapping plate, which separates the auricle from the 

 rest of the valve ; the colour also is fresh, although occasion- 

 ally deepened by an extraneous stain ; and the epidermis is 

 shghter : the j.mlh'fs, however, exhibit the most remarkable and 

 characteristic diiFerence ; the blade is oval and forked or 

 deeply indented and excavated in the middle at its outer edge ; 

 the outside is slightly gibbous and glossy or prismatic, and the 

 inside is fiat and of a dull chalky hue and cellular substance ; 

 the stalk never extends into the blade ; and the pallets in 

 this species are altogether more compact, and not laminar 

 as in the other species: sJieatJi usually less solid in pro- 

 portion to its size, and more tortuous ; it is irregularly annu- 

 lated in young specimens ; septa or internal plates arranged 



* Infesting ships. 



I 2 



