Introduction 



A comprehensive treatise on the diatoms of the United States is 

 yet to he published. Existing references dealing with the algae of 

 this country are either very provincial or shallow in their coverage 

 of the diatoms, therefore a large number of domestic and foreign publi- 

 cations must be consulted to find descriptions of all of our conmon 

 species. This is a formidable task for the beginning diatom student. 

 Descriptions of the diatom species which are most frequently encountered 

 at WPSS stations have been assembled in this illustrated guide which was 

 prepared to serve as a bench reference for biologists in our laboratory 

 who are being trained in diatom identification. The guide also contains 

 a glossary and generic key. The key was constructed with the beginner 

 in mind, and is based entirely on the shape and markings of the diatom 

 cell wall as observed in material mounted in hyrax. No attempt was 

 made to place the taxa in their proper phylogenetic order. Laboratory 

 personnel are encouraged to consult the taxonomic references for species 

 identification. 



We are indebted to Dr. Charles Reimer, Dr. Eugene Stoermer, and 

 Dr. Matthew Hohn for carefully reviewing the manuscript and making 

 many helpful suggestions. We are also grateful to the various authors 

 and publishers who have granted permission to use selected figures from 

 their publications. 



