68 1 he hish Naturalist. February, 



OUGOCHjETA. 



by rowland southern. 



The conditions prevailing on Lambay are not very favourable 



for Oligochaete worms. There is very little cultivated land, 

 and very few trees. Beyond a few wells and boggy patches, 

 there are no suitable places for the aquatic members of 

 the order. Worms are, however, able to exist under very 

 unfavourable conditions, and the collections have yielded a 

 large number of species. Of the 34 species found on Lambay, 

 15 are new to the Irish fauna, and 10 of these to the Britannic 

 fauna. Of the others, three are new to science. 



One of the most striking characteristics of the Lambay 

 Oligochsetes is the great variability exhibited by some of the 

 species, and this is especially the case among the Lumbricidae. 

 As a whole, the forms are of smaller size than on the main- 

 land. For instance, 10 specimens of Ltimbricus rubellus taken 

 at random had an average length of 74 mm. The average 

 length of an equal number from all parts of Ireland was 

 92 mm. The Euchytraeidse were also smaller than the 

 corresponding forms on the mainland. The chief variations 

 will be described under the various species. 



The only family of Oligochaetes which is sufficiently well 

 known in Ireland, to be of any value for comparative purposes, 

 is the Lumbricidae, or Earthworms proper. No fresh records 

 among these were made, even for Co. Dublin. The chief 

 point of interest was the absence of such common forms as 

 Helodrilus lo?igus, H. Eiseni, Lzwibricus papillosus, and L. 

 festimts, which all occur on the mainland, close to Lambay. 

 A closer examination, however, would be necessary before 

 inferences could be drawn from the absence of these forms. 



All figures (Plates 18, 19) are drawn from living specimens, 

 unless stated otherwise. 



List of Species. 



Those marked x are new for the whole Britannic area ; 

 those marked * are new for Ireland, but are already recorded 

 from Great Britain. 



