The rhinoceros faucial and laryngopharyngeal tonsils

The literature of mammalian splanchnology contains but a single reference to the tonsillar morphology of the Rhinocerotidae, viz. Owen's (1852) cursory description of the faucial (palatine) tonsil in an Indian rhinoceros {Rhinoceros unicornis). Herein a fuller account is given of the tonsillar formations present in the lateral food channel of another Indian rhinoceros specimen and of specimens of the Sumatran rhinoceros (Didermocerus suma‐trensis), the African White rhinoceros (Ceratotherium simum) and the African Black rhinoceros (Diceros bicornis). Attention is drawn to the invariable presence of tonsillar tissue in the rhinoceros pyriform fossa and to its frequent manifestation therein as an anatomically discrete and hitherto unrecognized organ, the laryngopharyngeal tonsil. This structure, functionally supplementary to the faucial tonsil, would appear to develop independently from the lympho‐thymic primordium of the embryonal third pharyngeal pouch. Its anatomy is described and its morphological significance is discussed.