158 



Jbranch of fcience exclufively, although the Ipecific diflinc- 

 tion will readily be afcertained by the Helminthologift on a 

 careful examination of the feveral animals. 



It is true our Serpula tuhularia is invariably round, or def- 

 titute of any carina, and in this refpect differs from mofl of 

 the others, which generally poflefs more or lefs dorfal ele- 

 vation ; but then it bears fo much refemblance to vermicU' 

 laris that the animal of the former being an Amphitrite is the 

 only abfolute criterion of di(lin6lion. The triquetra and the 

 other four fpecies whofe animals have been briefly defcribed, 

 run fo much into each other by pofiefling all the gradations 

 from that of being tricarinated, to fcarcely any trace even of 

 a dorfal ridge which unites them to the other two; and 

 thefe vary fo greatly in individuals, that to attempt a 

 divifion by the fhells would be only leading to error and 

 confufion : we muft therefore refer thoie who wifh to difcover 

 thefe feven fpecies of irregularly contorted Serpula to an 

 infpedlion of the animal inhabitants. 



It may not be foreign to the fubjedl, curforily to remark in 

 this place, that there appears no animal fo little underftood, 

 and fo unfuccefstully attempted to be defined by different 

 authors as that of the Linnaan Terebella ; and as we do not 

 think this clafs of animals with two plumous tentacula, and 

 furniflied with a pediculate operculum for clofing the aperture 

 of the fliell with which they are covered, accords with the 

 Linnaan charadlers of the Terebella^ we propofe that thefe 

 animals which are confined intireiy lo the Serpula, as far as 



difcovery 



