47 14 Proceedings of the Royal Irish Academy. 



97 - 2 per cent. ; Newport and Westport Bays, 63 species, or 78 - 7 per cent. ; 

 Bonn Harbour, 29 species, or 80 per cent. ; Ballynakill Harbour, 89 species, or 

 80 per cent ; Killary Harbour, 14 species, or 63 - 6 per cent. Westport and 

 Newport Bays and Ballynakill have 51 species in common. Thus the fauna 

 of Blacksod Bay shows greater resemblances to each of the other sub-areas 

 than these do to each other. This is probably due to the high average 

 suitability of the shores of Blacksod for maintaining a rich fauna, and the 

 absence there of any large tracts of abnormal ground such as would only 

 shelter a small and peculiar fauna. 



The species peculiar to ' Clew Bay ' consist principally either of those 

 forms living in 10-30 fathoms on clean sand, such as Achloe astericola, 

 Sthetielais limicola, iMmbriconereis impatiens, Onuphis britannica, Hyalinoecia 

 sicula, &c, or of small forms living on the " Polygordius ground." 



Notwithstanding the small numbers of species which are restricted to any 

 one sub-area, the number which occur in all the sub-areas is surprisingly 

 small, consisting, in fact, of only one, Nereis Dv/merilii. 24 species occur 

 in five out of the six sub-areas, and 40 species are common to the four sub-areas 

 in which the most work was done, namely, Blacksod Bay, Clew Bay, Newport 

 and Westport Bays, and Ballynakill Harbour. 



A consideration of the geographical distribution of the Polychaeta is 

 reserved for Part 67 of this series. 



Summary of Eesults. 



Of the Archiannelida, two species of Polygordius, both probably widely 

 spread on suitable ground, are added to the British fauna. The list of 

 Polychaeta comprises 249 species and 2 varieties. This is by far the largest 

 list of Polychaeta yet published from any limited area. The largest list 

 hitherto published is that of the Baron de Saint- Joseph, who found 210 species 

 at Dinard on the north-west coast of France. The fauna of this coast shows 

 great resemblances to that of our west coast. At St. Vaast-la-Hougue, a 

 favourite collecting-ground for the French naturalists, 165 species have been 

 found. In the report on the fauna of the Plymouth district, published in 1904 

 by the Marine Biological Association, 144 species are listed. At Wood's Hole, 

 Massachusetts, where the United States Bureau of Fisheries has a permanent 

 Marine Laboratory, the report on the survey of the district, published last 

 year, includes 135 species of Polychaeta. 



The large number of species found in Clew Bay is accounted for partly by 

 the richness of the fauna on our west coasts, and partly by the large amount 

 of time and care which was devoted to collecting them. 



It is impossible at present to institute comparisons of any value between 



