We consider a family of linearly viscoelastic shells with thickness 2ε, clamped along a portion of their lateral face, all having the same middle surface S = θ(ω) ⊂ IR 3 , where ω ⊂ IR 2 is a bounded and connected open set with a Lipschitz-continuous boundary γ. We show that, if the applied body force density is O(1) with respect to ε and surface tractions density is O(ε), the solution of the scaled variational problem in curvilinear coordinates, defined over the fixed domain Ω = ω × (−1, 1), converges in ad hoc functional spaces to a limit u as ε → 0 . Furthermore, the average u(ε) = 1 2 1 −1 u(ε)dx 3 , converges in an ad hoc space to the unique solution of what we have identified as (scaled) two-dimensional equations of a viscoelastic generalized membrane shell, which includes a long-term memory that takes into account previous deformations. We finally provide convergence results which justify those equations.