The spiral convolutions on a shell have often been associated with perfection and therefore plenty.
Dreaming of such an object would link with a primitive understanding of those things we can permit ourselves to have.
The conch shell was, and still is, used as a trumpet in ccrtain societies, hence it may be seen as a warning.
The conch shell links with the spiral (see Shapes).... Ten Thousand Dream Dictionary
The conch is also used as a trumpet and is therefore seen as a warning sign when present in dreams.... Dream Meanings and Dream Interpretation