POSTSCRIPT. 



" NULLA dies sine linca," was the recommendation of him 

 who brought into systematical arrangement the mighty ma- 

 terials of created nature : and long experience has taught 

 us, ' that each day is the disciple of that which has gone 

 before." 



In looking carefully over some fine specimens of the 

 Serpula tubularia, among which various other species were 

 entwined, we observed several of our Patella tricornis, and 

 P. Extinctorium attached to them, some of which closed up 

 the orifices of the tubes. This circumstance has led us to 

 the supposition that they may eventually turn out to be the 

 opercula or lids of different Serpulae. But as the animal 

 inhabitants of such as we examined were dead and shrunk 

 deep into the tubes, we could perceive no kind of attach- 

 ment. Anxious as we are to ascertain whether these are 

 actually specific productions, or merely the lids of other 

 shells, we can at present only issue our suspicions on the 

 subject, not being able immediately to refer to fresh and 

 living specimens of these Serpulae : and as our last proof 

 sheet is now before us for revision, we must in a few hours 

 close ail further communication through this channel. 



By the few conchological friends around us they have 

 been considered as Patellae : and it may be remarked, that 

 no author, as far as we know, has taken any notice of such 

 opercula ; not even Montagu, who has given much atten- 

 tion to the formation of the animals of this tribe. 



If therefore we are in error, it is an error which perhaps 

 better naturalists than ourselves might casually have fallen 

 into : and we are solicitous to point out the easy means by 

 which these singular productions may be arranged in their 

 proper place. 



z 2 Cardium 



