157 



1. With a fmooth, and (lightly concave tejlaceous termi- 

 nation or open ulum. 



2. With a tejlaceous termination armed with two or three 

 fpines in front. 



3. With a tejlaceous conical termination. 



4. With a fmooth termination, grooved on each fide for 

 the reception of two cirri placed at the bafe of the operculum, 

 which is corneous, furniihed with a bifid fiile. 



It is remarkable that amongft thofe authors we have been 

 able to confult, no mention is made of any animal belonging 

 to the Serpula cla fs with a teflaceous operculum, Muller ex- 

 cepted, ( for that part which has been confidered as a tongue, 

 or probofcis, is undoubtedly a pediculate operculum), who 

 befides figuring that with a fingle ftriated membranaceous 

 operculum, which v\'e have confidered as belonging to trique- 

 tra; has in his Zool. Dan. vol. iii. Tab. 86, given a figure of 

 that which we have defcribed to be the animal of vermicu-. 

 lans, M'ith a double infundibuliform operculum; and also a 

 third which appears to be our fecond animal above defcribed. 



That the fpecies of thefe irregularly contorted Serpula are 

 more numerous than have generally been confidered is evi- 

 dent, fince we find feven very difhndl animals inliabiting 

 lliells of this clafs fo extremely fimilar as to be totally unde- 

 finable by their habitations, and fometimes all grouped to- 

 gether in one contorted mafs. From the numerous fpeci- 

 mens examined, we fufp^-dl no conchological dillin61:ion can 

 ever be defined, fo as to make them fubfervient to that 



branch 



