A conspicuous accumulation of taste buds occurs in the rostral part of the plica sublingualis ("frenal lamella") of Alouatta and Aotus forming taste areas (area gustatoria) superficially situated in the oral mucous membrane. They are found in close vicinity to the orifices of the sublingual salivary glands, but are lacking in the aboral part of the plica sublingualis. They do not occur in all primate species studied. A taste area does not projects above the surface of the surrounding tissue like a papilla. The taste buds open not in crypts of furrows of the oral mucosa, but directly into the spatium sublinguale of the oral cavity proper. In the anterior part of the cavum oris proprium different kinds and very differentiated qualities of sensoral information are perceived (touch, olfaction, temperature). It is conceivable that the taste areas play an important role in perceiving fresh saliva, together with the other sensorial structures in this part of the mouth. This problem can be solved experimentally and by behavioral studies, In addition to its topographical relation to the tongue, the organon sublinguale of Callicebus is structurally very similar to the plica sublingualis of Aotus and Alouatta. Since a sublingua does not occur in New World monkeys, it can be concluded that this organ represents a plica sublingualis which became adherent to the undersurface of the tongue.