138 Proceedings of the Royal Irish Academy. 



(13) and figured (15), an Italian form Asternoseius, in whicli there is no 

 sternum ; the only resemblance between this and Thinoseius is the general 

 hardening of the body cuticle. There is little doubt that the loss of the 

 sternum in the adult is here a case of retrogression, as it is present and is of 

 the usual foiin in at least one nymph stage. 



H/VBITAT. — Found in company with the preceding species under decaying 

 seaweeds washed into the Orange Lichen zone. July, 1915. On anotlier 

 occasion it was found with numbers of the nymplui colcoptrata form among 

 damp sand and shells under a dry top layer in the same zone. Mr. A. D. 

 Michael has taken it on the seashore at Swauage (Dorset). 



Family ZERCONIDAE 

 THnozercon Michaeli Halbt. (PI. XXII, fig. 10.) 



1915 Halbert 25, p. 82. 



The male, female, and nymph of this interesting species were first found 

 under stones on an estuarine part of the seashore flooded by the tides at 

 Westport, in July, 1911. Snlwequently both sexes occurred under stones a 

 little below high-water mark on the south shore of Howth, April, 1913. 

 More recently Mr. Southern collect<»d it in the Orange Lichen zone at Lough 

 Hyne, on the Cork coast, November, 1916. I did not succeed in finding it 

 either at Ardfry or Malahide. 



Berlese was under the impression that this genus is synonymous svith 

 Iphidinychus, a South American form (15), and is so recorded by him (16). 

 He has recently seen specimens of Thiiiozercoii, and agrees with me that 

 they represent a very distinct genus (18). A figure showing the arrange- 

 ment of the ventral plates of the female is given in the present paper (fig. 10) ; 

 the presence of two paired sternal shields is of interest. There is consider- 

 able justification for making this remarkable form the type of a separate 

 family (see 25 ; for the present it is included in the Zerconidae. 



Family TTROPODIDAE. 



The identification of the four species of this family living liabitually 

 between tide-marks, and in salt marshes on the Irish coast, has given some 

 trouble, partly due to the fact that the " Uropoda orchestiidarum " of authors 

 included two species belonging to different genera. I believe the correct 

 names of the shore species liave now been placed lieyond doubt ; and a table 

 containing the more essential characters by wliicli they can be separated may 

 help to prevent furtlier confusion. 



