A Key to the Lizards of the United States and Canada

Abstract

The following key is based very largely on the writer's personal comparison of specimens in various collections, with special reference to those in the United States National Museum and the California Academy of Sciences. All genera have been examined critically. The herpetological literature has yielded much of value in the way of pointing out the differential characteristics of various forms, and the present writer, like any other who undertakes a similar problem in the biological field, finds himself deeply indebted to contemporary and previous workers. Cope and Van Denburgh merit special mention here. This key is purely artificial, being arranged for the convenience of its users, and not even a family sequence is maintained in the text. The ranges have been prepared (1) from published records, (2) from unpublished records held by the writer, and (3) from records verified by reliable herpetologists in recent correspondence. The known distribution of each species and subspecies is indicated, but future extensions of these limits (especially slight ones) may be expected. As Blanchard has stated in his useful Key to the Snakes of the United States, Canada, and Lower California, a species is conceived to be a population of similar individuals of similar habits, freely interbreeding and maintaining a high degree of constancy in most superficial as well as in all fundamental details throughout a generally considerable area. An unusual local emphasis on minor features is common, but it is not considered of taxonomic importance in separating species and subspecies. A subspecies is of the same nature as a species, except that it actually or potentially intergrades with members of one or more adjacent populations in areas where the two or more ranges involved approach or overlap. The intermediate zone of apparent intergradation delineated for two subspecies is often narrow, especially in regions like the Great Basin and the West Coast where sharp contrasts in environments are frequently presented, but the zone of intergradation may be wider in certain instances. It is often no easy task to apply the above criteria for the recognition of species and subspecies in the actual study of specimens from diverse areas, as any systematist knows. Common names are used to accompany scientific names throughout the following key. The scientific name of an animal is the same throughout the world, but the common name often varies with the locality or language. Standardized common names have been applied by the general Englishspeaking public to many lizards (such as hored toads for the lizards of the genus Phrynosoma), while many less-known forms have been given more or less appropriate names by specialists. The present list represents an attempt