1 08 Proceedings of the Royal Irish A cademy. 



may be found incorporated in Canestiini's well-known " Prospetto " 23 . 

 King has published an account of four species of Acarina found on the coast 

 at Millport, in tlie Firth of Clyde, with some interesting observations on 

 their life-histories. During the recent Clare Island survey a good deal 

 of attention was given to the littoral Acarina of the Mayo Coast, 

 and some new forms were brought to light (25 . Mr. E. Southern has 

 already published a very useful analysis of the large amount of shore- 

 collecting carrie<l out during this survey, more especially from the ecological 

 standpoint (R.I.A. XXXl . A recent paper by Hull (26) contains a number 

 of intertidal species found in the Tync Province and elsewhere in the North 

 of England. 



The species included in the following list are such as can be reasonably 

 considered as habitual denizens of the intertidal area. 1 am aware that many 

 other species found in the vicinity of high-water mark might liave been 

 included, more especially in the families Oribatidae and Tronibidiidae, but 

 for the present it seems best to include only such species as apjwar to live in 

 places directly afTectetl by the tides. A few of the mites recorded in this 

 paper, such as Gamasiui longieomis Berl., the two species of Aliens, and some 

 OrilKitids, require verification as inhabitants r.f the intertidal area. 



The question then ari.ses — are these intertidal si>ecies specially modified 

 to suit their peculiar mode of life? An examination of the genera repre- 

 sentee! shows that a fair percentage of them are characteristic of the shore, 

 and when this is the case they are represented by but lew, sometimes only 

 one spocies; such are Halolaelaps, IJydrogamasus, Thinozercon, and others. 

 Yet, although these genera and species often possess peculiarities in the 

 structure of their dorsal and ventral plates and in other characters, it cannot 

 be said that they exhibit any striking uKMlifications lo suit them for even a 

 .senii-a<^uatic life. For ini<tance. it is in the breathing organs that we should 

 ex|tect to find modification, but as far as one can judge these organs are not 

 exceptional in the intertidal species. On the other hand, the possession of a 

 smooth shining epidermis, or a covering «if fine hairs, to jirotect the creatures 

 from wet surfaces would l»e of great use, for the reasons given below, and 

 these are characters which the majority of them possess ; in common, however, 

 with a great many purely terrestrial species. A modification in the foim of 

 the tarsi and ambtdacra certainly does occur in a few genera (Hydrolaelaps 

 and others), and we find a similar change in these stnictures in certain 

 species of the t«iTestrial acari which fretjuent very wet places (25) away from 

 the seashore. 



It was at first believed that these intertidal mites lived freely on the 

 shore, and on the approach of the tides betook them.selves to crannies and 



