snakes and lizards have a strong superficial resemblance to earthworms. One 

 may judge of the confusion that exists, even in the vertebrates, when he finds 

 that one salamander is commonly called the Congo Snake and another the 

 Mud Eel, and that one of the legless li2;ards is known as the Glass Snake while 

 another lizard masquerades as an amphibian under the names of Horned Frog 

 and Horned Toad. The keys accompanying this chapter are designed to 

 direct the student to succeeding chapters for further identification. The 

 associated plates illustrate forms that are not readily distinguished or assigned 

 to their proper groupings. 



In the keys two alternatives, definitely contrasting, are ofFered at once, 

 so that the characters can be quickly weighed one against the other and the 

 decision made without any turning of pages. At the end of the choice taken 

 is given the number of the next set of alternatives to be considered, and so 

 on, until, instead of a number, there appears the scientific name of an animal. 

 The fact of individual variation must be kept in mind in any attempt at 

 identification. Between such extremes as albinism and melanism, giantism 

 and dwarfism, there is a wide range. The keys must naturally be based on 

 normal, adult, average or typical specimens. Whenever possible, therefore, 

 several animals of the kind to be identified should be examined or, if only 

 one specimen is available, the possibility of its being somewhat abnormal or 

 immature should be considered. 



Following each key is a list of references, one or more of which the reader 

 should then consult in order to verify his identification. This list does not 

 begin to include all the works upon the group but merely those that the 

 author believes will be most useful in aiding in the verification of the name. 

 Check lists of the various groups of animals known to occur within the local 

 area are often available from state or city museums, state natural history 

 surveys or state academies of science. If these cannot be obtained, there are 

 still several invaluable periodicals where such lists, at least of the vertebrates, 

 are often published. Chief among these are Copeia for fishes, amphibians 

 and reptiles, The Au\ and The Auduhon Magazine (formerly Bird-Lore) for 

 birds and The Journal of Mammalogy for mammals. These lists are very 

 useful in indicating which animals may be expected in a given locality and 

 should be consulted wherever it is possible. 



Protozoans, rotifers, small crustaceans and other minute, free-floating, 

 aquatic forms constitute a group of organisms known as plan\ton. For identi- 

 fication of these and other minute creatures, a microscope is necessary. Since 

 both size and motion appear greatly magnified under the microscope, some 

 method of slowing down the living animals while they are being examined 

 is desirable. A very weak solution of glycerine in water may be substituted 

 for the drop of plain water in which the creatures are ordinarily mounted 

 for examination. Much use should be made of lighting adjustments. For 



