46 4 Proceedings of the Royal Irish Academy. 



Monospilus dispar, Cyclops bicolor, C. varicans, Canthocamptus lucidulus, Noto- 

 dromas moriacha, Ilyocypris bradyi, Limnicythere sancti-patricii, and Cytlwridea 

 torosa. The first and third named at least may be considered as typical 

 •' lowland " species, for they are rarely if ever found in mountainous and 

 moorland districts, and, taken in connexion with the other species enumerated 

 and the rarity of such forms as Acantholeberis curvirostris and Alonopsis 

 elongnta, clearly indicate the influence of the different physical conditions of 

 this district as compared with the others. 



The Louisburgh-Croaghpatrick list exhibits the following peculiarities : — 

 Diaphanosomct brachyurum var. nasuta, Daphnia hyalina var. galeata, Simo- 

 cephalus exspinosus, Ceriodaphnia reticulata, and Bosmina longicornis. I am 

 indebted to Mr. Kane for all the records from this district except those from 

 Croaghpatrick itself. The species recorded from the latter mountain are as 

 follows : — Acantlioleberis curvirostris, Alona rustica, Ghydonis sphaericus, Cyclops 

 viridis, C. fuscus, C. prasinus, and Canthocamptus zschoklcei. These I obtained 

 by collecting in bog-pools at various heights up to about 1500 feet, and by 

 washing mosses taken from the sides of the small streams. Acantholeberis 

 curvirostris, Chydorv.s sphaericus, ■ and Cyclops prasinus were characteristic 

 of the former, Alona rustica and Canthocamptus zschokkei of the latter. 

 Mr.- Kane's collections were made about Louisburgh, and as far west as Boonah 

 Lough, and as far south as Doo Lough. The Copepoda and Ostracoda were 

 only partially studied. 



Taking the district worked over by the Survey as a whole and comparing 

 it, so far as the imperfect records allow, with the rest of the counties of 

 Mayo and Galway, the most noticeable differences are to be found in the 

 absence from the former of a number of typically plankton species of 

 Gladocera and Copepoda (e.g. Bosmina coregoni, Bythotrephes, Leptodora, 

 Diaptomii-s laticeps, &c.) and a considerable number of Ostracods. The 

 explanation of the missing plankton forms is almost certainly to be found 

 in the fact that the larger lakes of the survey area were not examined, 

 while the larger number of Ostracods in the list from the remainder of 

 Mayo and Galway is accounted for by the attention devoted to this group, 

 especially in Connemara, by such well-known authorities as Brady, Robertson, 

 and Norman. 



Combining the survey results with the records from the other parts of 

 Mayo and Galway, we obtain for the first time in Ireland a list from a fairly 

 large and compact area (practically the "West of Ireland" par excellence) 

 showing some signs of approaching completeness. The total of 115 species 

 compares not very unfavourably with the numbers recorded from some much 

 more thoroughly worked districts in England and Scotland, and considerably 



