6co [Proc. B.N.E.C., 



of Lough Neagh since many samples of schist, granite, Carbon- 

 iferous sandstone, quartzite, and pebbles from the Old Red 

 conglomerates were found amongst the debris of local rocks. 



Instead of pursuing its natural course down the valley at Aghalee,. 

 the canal turns southward and enters Lough Neagh by Ellis's Cut. 

 The object of this detour is not obvious at present, but we must 

 remember that in the days when the canal was constructed the 

 waters of the great lake stood at a considerably higher level and 

 the now cultivated flat between Aghalee and Portmore was but a 

 low and often-flooded marsh, through which it would be difficult 

 to make a waterway. An interesting feature of the district visited 

 is to be found in the shell-marls which in many hollows underlie 

 the cultivated fields. At the close of the Glacial Period all these 

 hollows nestling among the drumlins held small lakes, and these 

 marls were laid down during this epoch. Through the natural 

 deepening of their outlets and the gradual filling up of their 

 basins by vegetation the smaller of these lakes have now dis- 

 appeared, but their history can be traced in the marls, which 

 contain many fresh-water shells, plant seeds, and other objects of 

 interest to naturalists. Since the deposition of some of these 

 marls many additional species would appear to have arrived in 

 the district, crushing out in the struggle for existence some of 

 those which were dominant during the formation of the deposits. 

 The best example of the disappearing fauna is perhaps Planorbis 

 glaber, a fresh-water shell, which is abundant in these marls, while 

 at the present time it is confined in the counties of Antrim and 

 Down to a few isolated habitats, where it still lingers in spite 'of 

 the competition of stronger species. One of the retreats of this 

 ancient species is to be found in the hot mill-ponds in the city of 

 Belfast, where it appears to be free from annoyance by its com- 

 petitors, and is often abundant. The construction of the canal 

 between the basin of the Lagan and Lough Neagh has no doubt 

 aided the dispersal of some species, such as Limtnea auriculana, 

 Anodonta cygnea, and Spheerium lacustre, which, though frequent 



