THE NAUTILUS. 



Vol. XXXV JULY, 1921. No. 1 



RIVER BARRIERS TO AQUATIC ANIMALS. 



BY CALVIN GOODRICH. 



Contending that the genus was purely a creek form, Dr. 

 James Lewis 1 questioned the existence of Goniobasis in the 

 Holston river. Tryon, 2 with little waste of good-nature, re- 

 torted that Dr. Lewis was in no position to know about this, 

 since the information upon which the assertion was based had 

 to do with only twenty-five miles of the Holston. 



Dr. Lewis seems to have glimpsed a fact in the distribu- 

 tional history of Gowiobasis, but not all of the fact. The 

 genus does exist in parts of the Holston, but it is where creek 

 conditions obtain or river conditions are no more than begin- 

 ning. It ceases to live in the true river. The twenty-five 

 miles which had been painstakingly explored by Lewis's cor- 

 respondent were apparently below the line of creek charac- 

 teristics, within the barrier across which Goniobasis of the 

 region could not go. 



Dr. Paul Bartsch, 3 describing the restrictions which the 

 sediment-laden Missouri places upon the distribution of the 

 Uni<mid<T, remarks: "We have, therefore, the curious eondi- 



1 Amer. Jour, of Conchol., vol. vi, p. 216. 



2 Ibid., vol. vii, p. 86. 

 s Nautilus, Dec., 1916. 



