Acari. 421 



that genus which Piersig has given in his great work "Deutschlands 

 Hydrachniden". 



He also points out that there is every reason to believe that 

 Greenland harbours several species of Hydrachnidæ and that the 

 negative evidence furnished by the researches made hitherto is not 

 conclusive, no investigations having been made by experts on the 

 group. 



The discovery of a Hydrachnid by Mr. F. Johansen rendered it 

 imperative to reexamine Thorell's type specimen in order to settle 

 definitely the questions mentioned above. 



Owing to the extreme courtesy of Professor Y. Sjöstedt, the 

 curator of the entomological department of the Government Museum 

 in Stockholm, I was able to examine the type specimen of L. fabricii 

 and to make a miscroscopical slide ot the legs and the gnath- 

 osoma. 



Of Thorell's TrombidiumAarxsi there is, on the other hand, 

 no specimeu in the collections, so that we will never be able to 

 learn what species it was. 



The reexamination of L. fabricii with the aid of Sig. Thor's 

 excellently illustrated and very detailed descriptions of all the well- 

 known species of the genus Lebertia (7 — 10) has proved beyond 

 doubt, that that is not the species found by the Danmark-Expedi- 

 tion on the N. E. coast of Greenland, but that there are two different 

 species in Greenland, even belonging to different subgenera. 



L. fabricii is a Pseudoleberta and according to Sig. Thor, who 

 has been kind enough to examine the figures of the species which 

 I sent to him, it is a distinct species, whether more closely related 

 to the glabra-gvoup or to the maculosa-group , however, he could 

 not tell. 



As to the larva figured by me in "Fauna arctica" and which I 

 believed to be the larva of Thorell's species. Sig. Thor who has 

 also examined this form is inclined to place it in the genus 

 Arrhenurus or some closely allied genus. 



If this supposition is true, there are, consequently, still more 

 hydrachnids in Greenland which the researches, hitherto made, 

 have failed to discover. 



Lebertia. 



Subgen. Pilolebertia S. T. 

 P.porosa S. T. 



Localities: Under the ice near the shore of a small freshwater- 

 lake, near the "Bastion", Hvalrosodden, 25th May 1907; in a swamp 

 betAveen "Rypfjældet and "Hvalrosodden", 4th and 5th July 1908. 



