1. This key includes all the species of reptiles known to occur in those states of the United States and provinces of Canada lying entirely or in part west of the Rocky Mountains. Characteristic habitats are indicated for each species. However, it must be remembered that individual reptiles will wander some distance into nearby ecologic situations. Naturally, a species is to be expected only within the general area indicated on the range maps.
Habitats are listed on the border of each page opposite the name of each species...
In using the key you may still encounter difficulty when dealing with examples of the genera Eumeces, Cnemidophorus and Thamnophis. Careful examination with a magnifying glass or microscope whenever possible will result in accurate identification in most cases. In any doubtful case be sure to check the species distribution map and also the habitat. For more complete information see the publications listed at the end of this booklet.
HOW TO USE THE KEY The key is a simple and easy method for determining the name of any specimen of western reptile. To use the key begin at number 1, which gives two alternates:
1a. Body encased in a rigid shell. Turtles-------Page 2
1b. Body not encased in a shell.-----------------Page 15
If, for example, the specimen at hand is a turtle, it will agree with 1a., so proceed to the number (in this instance no. 2) given at the right. Here again two are found and again one is selected. Continue in this manner, carefully studying the characteristics of your specimen at each couplet until you arrive at the name of the reptile in hand. (from the Introduction)