Shell is one of the main features of mollusks, and useful to protect their body from predators or severe environments. However, it is not known what kind of signals regulates their shell formation. We examined dpp expression patterns in the pond snail Lymnaea stagnalis, and analyzed its functions under the presence of the Dpp inhibitor, dorsomorphin, in order to understand developmental mechanisms of shell formation in gastropods. The dpp gene is expressed in the right half of the circular area around the shell gland at the trochophore stage and at the right-hand side of the mantle at the veliger stage in the dextral snails. When the embryos were treated with dorsomorphin at the trochophore and veliger stages after the shell gland formation, juvenile shells grew to a cone-like form rather than a normal coiled form. These results indicated that dpp plays important roles in the formation and coiling of the shell in this gastropod species. We also examined dpp expression patterns in the limpet Patella vulgata. In this meeting, we report these results and discuss the roles of dpp in gastropod shell formation, especially in shell coiling.