VOL. 54, NO. 1, JANUARY 1978 
25 
tation near the edge of a stream. 
Presently there are two rivers from which both E. inermis and E. 
infrequens are known, the Weber River in Utah and the Teton River in 
Idaho. In both cases the species appear to be allopatric with E. 
inermis occurring downstream from E. infrequens. 
Acknowledgements 
The author would like to thank G.F. Edmunds, Jr. and D.N. Alstad 
for their advice and assistance; also W.P. McCafferty and R.K. Allen 
for reading and commenting on the manuscript. 
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