Anguid lizards are found on most continents and most have strongly reduced limbs. The alligator lizard of western North America is exceptional, in that it has relatively well-developed limbs and moves in a similar way to most other lizards. Since 1974, an extensive series of reports has been published on the structure and response activity of the hearing organ of the alligator lizard, Gerrhonotus multicarinatus, a member of the Anguidae. This is mainly work from the laboratory of T.F. Weiss, Massachusetts Institute of Technology. More recently, interesting parallels to the data from the alligator lizards have been described in the (not very closely related) iguanid granite spiny lizard, Sceloporus orcutti. Iguanids are, with very few exceptions, restricted to the new world. Sceloporus and similar lizards are typical insect catchers of warm, dry regions of N. America. As mentioned in Chapters 1 and 4, there are strong anatomical similarities between the ears of iguanid, agamid and anguid lizards. The present chapter also describes similarities in the physiological data.