47 



If we look at many kinds of Murex, we find the lip appears always hard and fully formed, 

 how is this? It would almost appear that when the animal wished to enlarge its shell, it must 

 do so by a spasmodic growth of a quarter or half a circle, as shown by the number of the lips 

 which can be traced on the shell. Probably, during this growth of the shell, the creature may 

 remain in some corner till the shell is hardened, as the shells which we see have the fully- 

 developed lip ; this is a curious fact. In some species, when the lip is once formed, whatever 

 size the shell may be, its growth is completed. Some species never show the marks of a former 

 hard lip, whilst in other species the size and growth of the shell can be traced by the regular 

 formed lips which have been overgrown ; but in the kinds I refer to, one never meets with 

 one with the lip in an imperfect state. 



Then again, the genus Trocus, of which our common silver shell is an example. As a rule 

 all of each species are symmetrical; one kind however is so eccentric as to gather on its shell 

 stones or pieces of broken shells ; but how is this managed, as the stones or other substances 

 must be gathered when the shell is soft? but when once stuck on they give the creature's 

 habitation an irregular and unique appearance altogether. 



