In spite of important differences in shape and appearance, the tongues of Pontoporia blainvillei, Neomeris phocaenoides and Delphinus tropicalis present certain common characteristics. None have papillae resembling, even slightly, those described in other mammals [ARVY, 1959-1962]. They are all covered by a stratified malpighian epithelium that is finely keratinized. They all contain the same type of salivary glands which, anteriorly, resemble swollen pouches and are intradermic and, posteriorly, become more elongated and penetrate between striated muscular bundles. Their secretion is aldanophilic and it reacts vividly to the periodic acid-Schiff stain.
The comparatively rare dermic papillae that occur towards the front are short and wide. Towards the back where they are present in large numbers, these papillae are long and narrow and they form numerous digitations containing a large number of vessels curled round in loops that are flush with the lingual surface. The large tongues of Neomeris phocaenoides and Delphinus tropicalis have high, regularly or less regularly grooved, lateral surfaces. Each groove contains a large number of dermic digitations that form an important vascular layer which is probably the site of heat and other exhanges with the exterior environment.