INTRODUCTION 



Among the numerous interesting zoological 

 specimens brought back by Professor Kiikenthal 

 from East Spitzbergen on his return from the Bremen 

 Expedition (1889),^ was a small species of Apus — 

 presumably Lepidurus glacialis (Kroyer). Professor 

 Kiikenthal very kindly handed these specimens to 

 me for examination. By the kindness of the Rev. 

 Canon Norman, I also received Greenland specimens 

 of Lepidurus glacialis (Kroyer), and from Professor 

 Leche, of Stockholm, specimens of the Lepidurus 

 glacialis found by Professor Nathorst in West Spitz- 

 bergen ; Professor Mobius, the director of the Berlin 

 Natural History Museum, generously sent me speci- 



^ Dr. Alfred Walter, to whom this book is dedicated, was Professor 

 Kiikenthal's companion during this expedition. He died shortly after 

 his return. 



