229 
VERTEBRATES EXAMINED 
The present study is limited to the parasites of three of the major 
groups of the Vertebrata; namely, Pisces, Amphibia, and Reptillia. No 
records of Acanthocephala from water-birds of the locality under con- 
sideration are available. It should be kept in mind, however, that most 
of our water-birds are migratory, and that consequently their parasitic 
fauna is not necessarily as characteristic of any restricted area as is the 
fauna parasitizing other fresh-water vertebrates. The writer (1918) has 
published the results of studies upon the Acanthocephala of birds from 
various parts of the United States. Little is known of the actual geo- 
graphical distribution and restriction of the Acanthocephala parasitic in 
birds, and it is consequently unsafe to infer the presence of any given 
species of Acanthocephala in the Illinois River merely because it has been 
recorded from a species of bird whose range may include this locality. 
Inferences of this type have been common in the literature on parasi- 
tology, and they are responsible for many incorrect statements regarding 
the distribution of the parasitic fauna. 
