Cryptovolcanic and allied structures cut strata of Passage Group, Upper Limestone Group, and Lower Limestone Group age on the coast between Port Seton and Aberlady. Two structures in Gosford Bay and one on Port Seton beach are oval in form; others at Kilspindie and Port Seton reef are linear in character. One of the structures at Gosford Bay, together with those at Port Seton reef and Kilspindie are breccias with tuff matrices containing basaltic glass. No brecciation or tuff occurs in the structures on Port Seton beach and the other Gosford Bay occurrence; for these a volcanic genesis is inferred by association and by comparison with records elsewhere; they are assumed to occur at a stratigraphic level above the upper limit of tuff penetration.