A multi-ply paper web is formed by bringing a top ply liner into ply-bonding engagement with a base ply web (W.sub.B) traveling on a base ply forming wire (36). The top ply liner (W.sub.T) is formed between two co-running forming wires (10, 20) in a convex upwardly/concave downwardly curved, substantially horizontal forming zone. Dewatering in the forming zone is effected by applying sub-atmospheric air pressure solely beneath the lower surface of the top ply liner (W.sub.T) being formed. Water is removed from the upper surface of the top ply liner (W.sub.T) solely by wire tension, gravity and centrifugal force created by passing the co-running forming wires (10, 20) over the convex upwardly curved path of travel. This permits a greater concentration of pulp stock fines to remain in the upper surface of the top ply liner (W.sub.T) to effect greater ply-bonding affinity with the base ply (W.sub.B) when the two plies (W.sub.T, W.sub.B) are brought together and bonded.