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HYDRACARINA: THE GENUS OXUS KRAMER. 



By Charles D. Soar, F.L.S., F.R.M.S. 



{Read March lUh, 1919.) 

 Plate 1. 



1877. Oxus P. Kramer. Arch. Naturg., vol. xliii. page 240. 

 1880. Pseudomarica Neuman. SvensJca Ah. Handl. New series, 



vol. xvii. No. 3, page 70. 

 1901. Pseudoxus Sig Thor. Norges Hydrach, vol. i. page 18. 



This is one of tlie four genera of the sub-family Lebertiinae. 

 It has a number of species, three of which have been recorded for 

 the Britannic area : 0. plantaris Sig Thor, 0. strigatus Mull, 

 and 0. ovalis Miill. The type species of this genus 0. quadri- 

 parus Pier. (= ohlongus Kramer) has not been found in the 

 Britannic area, so I propose to use 0. plantaris Sig Thor in its 

 place. It is by far the largest species of the three, and I was 

 fortunate in having quite a number of specimens sent to me 

 alive by Mr. G. T. Harris, of Sidmouth, who washed them out 

 of some sphagnum found in a bog on Dartmoor in 1918. In 

 the original descriptions by Sig Thor and in that of Mr. Halbert 

 only the female is mentioned ; but in the collection of living 

 specimens sent me by Mr. Harris besides females there were 

 several males and one nymph included, and it is from these the 

 description is taken. 



The generic characters of Oxus are : Body an elongated oval, 

 dorso-ventrally compressed ; skin soft, granulated or striated ; 

 dorsal surface without band or furrow as in Frontipoda and 

 Unaphiscus. Epimera fused into one piece and covering the 

 greater part of the ventral surface. Legs close together on 

 anterior part of body, as in Frontipoda ; fourth pair without 

 claws. Genital area partly enclosed by epimeral plate. Male 

 and female very much alike. 



