Fig. 7. A simple model of lizard ear directionality (Fletcher 1992). (A) Diagram of a transverse section of a lizard head (Sceloporus; redrawn and altered from Wever, 1978). TM, tympanic membrane; C, columella; ET, Eustachian tube; MEC, middle ear cavity; RW, round window; OW, oval window. (B) The electrical analog circuit (Z_V impedance of mouth cavity, Z_T impedance of tympana, P₁ and P₂ sound inputs; details of parameters in Materials and methods). (C) Vibration velocity spectra for ipsilateral (red curve) and contralateral (black curve) sound directions (compare Fig. 2). (D) Cylinder surface plot of the model response (compare Fig. 3).