The very distal part of the chicken basilar papilla was investigated by light and electron (scanning and transmission) microscopy. The rostral tip of the basilar papilla has a lenticular area with atypical sensory hair cells which are more similar to vestibular than to auditory cells. The structure of the lenticular area appears to be suitable for vestibular function or, more likely, for auditory perception at very low frequencies. Several hypotheses can be proposed to explain this very peculiar portion of the avian cochlea. It is difficult to consider it a continuously growing area since it remains stable in adulthood. A better explanation would be that there is an incomplete ontogenetic or phylogenetic process.