Biological Papers. 157 



always upstream. When they had a nest dug out to suit their 

 requirements they would lie down in the excavation quite still 

 for quite a while. 



Just below the riffle used for nest-building there was another 

 pool only two or three feet across, below which was another 

 gravelly riffle, but our fish did not resort to these portions of 

 the stream so far as was observed ; but a few darters, Efheos- 

 toma arcuscelestis, were seen here. This latter species of fish 

 seems to confine itself in spawning to riffles having a smooth 

 clay bottom covered more or less with sand and gravel. 



