12 ' The Irish NahU'alist. January, 



assemblage of species associated together owing to some 

 common tie such as physical environment ? If the group 

 were a distinct element its Irish distribution would lead us 

 to expect that it belonged to Forbes' " Galilean " type,^ 

 but its English distribution does not bear this out. With the 

 exception of B. minutissimus , none of the species of these 

 south-eastern Irish water-beetles are concentrated in the 

 west or south-west of England, and some of them are even 

 rare on that side of the country. For instance, H. ohlongns 

 has been once recorded for South Devon - and not from 

 anywhere else in the west or south-west. Similarly Rh. 

 Grapii has once been found in south Lancashire many years 

 ago,^ otherwise nowhere in the west or south-west. H. 

 nanus was recorded doubtfully for Exeter (S. Devon) by 

 Pariitt in 1867, but otherwise there is no record for it west 

 of East Gloucester. 



But the group is not an isolated one ; there are species 

 which, though not confined to or specially concentrated in 

 the south-east are, nevertheless, absent from or rarer in the 

 west, and which are therefore intermediate in their dis- 

 tribution between the south-eastern group and the group 

 which is generally distributed throughout Ireland. Thus the 

 south-eastern group seems to be merely a part of what we 

 might call — following Watson's nomenclature for Britain — 

 the " Irish " type. 



Examples could be chosen showing all stages of distribu- 

 tion across Ireland, but a few will serve to show intermediate 

 range. A. jemoralis, a northern species, absent from the 

 north of Ireland, has been recorded from Limerick and 

 Roscommon outside our district. H. nuhilus ranges as far as 

 East Donegal in the north. Rh. notatiis and exoletus, H. 

 longior, pulchella, atricapilla and Britteni have a more 

 extended range, reaching far across the central plain in 

 some cases to Roscommon. Symbol maps of two of these 



I The Geological Relations of the Fauna and Flora of the British 

 Isles, &c. Mem. Geol. Survey, I., 1846. 



2 Victoria County History, 1906. 



3 Vide Ellis, J. W. : The Coleopterous fauna of the Liverpool district, 



Proc, Liverpool Biol. Soc., vols, ii., & iii., 1889. 



