Serpents lack an external ear, a tympanic membrane, a tympanic cavity, and a Eusta- chain tube. These negative but very significant characteristics are seen phylogenetically, especially in connection with the reduction of the eye (Le., Nopsca, 1923; N.B., today Pachyophis is grouped together with the Simoliophidae, furthermore Mahendra, 1938; Walls, 1940, 1942; Bellairs and Underwood, 1951). Other authors mention these cha- racteristics in connection with characteristics of ingestion (Berman and Regal, 1967). They claim that the formation of a tender tympanic membrane and a tympanic cavity is...