The funnel of Gammarus oceanicus extends as a fold of the foregut wall into the midgut lumen. It comprises an anterior segment, to which both foregut epithelium and cuticle contribute, and a posterior segment that lacks the epithelium. The latter segment consists of two layers of foregut cuticle that are in close contact and extend distally beyond the point where the foregut epithelium turns back on itself; contact between the two cuticular layers develops as the epithelium retracts from between them, in postmolt. Light microscopy does not consistently distinguish between the funnel's posterior segment and the peritrophic membrane found within mid- and hindguts; however, their ultrastructural organizations are distinctly different, and an origin of peritrophic membrane from the funnel of some amphipods, as suggested in the literature, is not the case for Gammarus oceanicus. Scattered within the posterior segment cuticle are clusters of short, highly curved, electron-lucent rods. Such features have not been described from other crustacean cuticles. However, rather than being novel structures, they are interpreted as artifacts produced by sectioning of the abundant chitin macrofibrils of the cuticle.