K^:o^vLEDGE of the hydrachnidae. 281 



forming but one distinct pair. Type : Pseudomarica formosa 

 Neuman.* 



This genus has been instituted by Neuman for the distinction 

 of a form which he thinks may be possibly identical with Marica 

 chlonga of C. L. Koch, and which is distinguished from the 

 typical members of such genus by its depressed instead of com- 

 pressed body, additional characters of distinction being afforded 

 by the scattered setae developed upon the margin of the body 

 and from the fine posterior edges of the genital plates. Other 

 depressed forms awaiting the examination of modern investigators, 

 and that will apparently have to be relegated to the same genus, 

 are the Marica viresce7is, 21. lopida, M. strigata, M. ohlouga, and 

 M. confinis of C. L. Koch. In the writer's opinion, Pseudomarica 

 must be regarded as one of the most interesting and important 

 generic forms of the Hydrachnidae, it coinciding more nearly in 

 general structure and configuration with the larval conditions of 

 this family group than any other known type, and in which 

 connection it would seem to occupy the position of a primitive 

 form or archetype. The developmental phenomena, which with 

 respect to neither this nor the succeeding genus have been so far 

 observed, will probably prove of interest. No representative of 

 the genus Pseudomarica has, up to the present time, been obtained 

 by the writer in this country. 



Genus 2. Marica C. L. Koch. 



Body laterally compressed, the cuticular surface indurated, 

 with a rectilinear suture-like ridge developed down the centre 

 of the dorsal border ; all four pairs of legs decussating from the 

 anterior extremity of the body, their epimera united so as to 

 form a continuous sternal shield ; genital plates elliptical, with 

 a differentiated external border, beset with numerous setae and 



* Pseudomarica, Neuman. This genus is now known as Oxus, Kramer, 

 who first used this name in 1877. Neuman did not introduce Pseudo- 

 marica until 1880, and the type species P. formosa is really Miiller s 

 species which he called Hydraclma strigata ; the proper name is Oxus 

 strigatus, Miill. Saville-Kent also mentions in this paragraph besides M. 

 strigata two others of Koch"s names which are only synonyms of the 

 same mite, M. ohlonga and M. confinis. We have now four species recorded 

 for the Britannic area ; 0. strigatus, Miill. ; 0. ovalis, Miill. ; 0. longisetvs, 

 Berlese, and 0. jylantaris, Sig Thor [C.D.8.] 



