Calcareous Pebbles formed by Algtz* 83 



Nitzschia Hnearis, Sm. 



sinuata, Grun. 

 Pinnularia commutata, Grun. 



rupestris, Hantzsch. 



appendiculata, K. 



subcapitata, Greg. 



Rhaphoneis oregonica, E. (doubtful). Rare. 

 Pleurosigma attenuatum, Sm. Scarce. 

 Pleurostauron Smithii, Grun. One specimen seen. 

 Synedra delicatissima, Sm. 



E. GROVE, 



