Ampullary organs are found on the head and body of the African knife fish Xenomystus nigri. Each organ consists of a duct connecting the basally located sensory cells with the surrounding water. The sensory epithelium is found in a chamber situated in the basal part of the epidermis, which most often is somewhat depressed into the dermis. Each organ contains four to eight sensory cells separated from each other by supporting cells. Both sensory and supporting cells are surrounded by mantle cells. Apically, the pear-shaped sensory cells have a tuft of 40 to 60 microvilli and between these a short cilium; basally they are innervated by one large afferent nerve ending. No efferent endings have been observed.