igil] NORDAMERIKANISCHE HYDRACHNIDEN. 281 



A REVISION OF MY "NORDAMERIKANISCHE 

 HYDRACHNIDEN "1 



By F. Koenike, Bremen. 



Translated by E. M. Walker, Biological Department, University of 



Toronto.* 



A fuller knowledge of the Hydracarine genera Eylais and Lebertia 

 has necessitated a fresh diagnosis of the Canadian material on which 

 my paper was based. As regards Eylais I recognized while working 

 over the collection of water-mites made by Professor Voeltzkow in 

 Madagascar, Aldabra, etc.,'^ that species were present that were readily 

 distinguishable from E. extendens (O. F. Miill.). The recognition of 

 this fact led me some years ago to work over the Canadian Eylais ma- 

 terial, and as a result three new species (£. falcata, E. desecta and E. 

 triangulifera) were established and briefly described.' In the present 

 paper these species are more fully characterized and figured. A fourth 

 new species of Eylais has also recently come to light, which I have dedi- 

 cated to the American naturalist. Miss Ruth Marshall, in recognition 

 of her admirable work on her native representatives of the genus 

 Arrhenurus. 



What has been said of the genus Eylais applies also to the genus 

 Lebertia, for our knowledge of which great credit is due to Dr. Sig. Thor. 

 Under the material formerly referred to Lebertia tau-insignita (Leb.) I 

 can now distinguish three species, one of which I have named after the 

 eminent North American Hydracarinologist, Prof. Robert H. Wolcott, 

 and a second after Dr. J. B. Tyrrell, who collected the Canadian water- 

 mite material which formed the basis of my paper of 1895. I am also 

 specially indebted to Dr. Tyrrell for his kindness in placing at my dis- 

 posal his collection of preparations of the Hydracarine material here 

 treated of. 



•The translator wishes to express publicly his thanks to Prof. Robert H. Wolcott, 

 for many helpful suggestions in the translation of Herr Koenike's paper. 



* F. Koenike, Nordamerikanische Hydrachniden. Abh. Nat. Ver. Bremen, 1805, 

 XLII Bd., S. 167-266, Taf. I-III. 



' F. Koenike, Hydrachnidenfauna von Madagaskar und Nossibe. Abh. Senckenl. 

 naturf. Ges., 1898, XXI Bd., S. 297-435, Taf. XX-XXIX. 



' F. Koenike, Zur Systematik der Gattung Eylais Latr. Abh. Nat. Ver. Bremen. 

 1897, XIV Bd., S. 279.295. With 6 fig. 



