64 The Irish Naturalist. April, 



Possible Hunting-Grounds for the Characeae. 



It is to be hoped that Canon Bullock- Webster's want of success in 

 hnding Characeae in the Rosses will not prevent his further visits to tliat 

 district of Donegal. To the north of Burton Port lies several lakes with 

 sandy bottoms all of which, so far as my recollection serves me, shelter 

 these plants. Canon Bullock- Webster seems to have been unaware of 

 these lakes and appears to have stopped his quest at Mullaghderg, just 

 as he was approaching them. The lakes 1 refer to are those on Cruit 

 Island, which is a peninsula at half-tide, and Carnboy Lough on the Car- 

 rickfin peninsula opposite Bunbeg. 



North of these there lies in the dunes near Derrybeg another lake known 

 by the inhabitants as Lough-na-Carrickagh, which is the Lough Acartan 

 of the Ordnance map. In Co. vSligo the lakes at Rosses Point are, I 

 think, choked with Charas ; and still further southw^ard is the great 

 series of lakes that lie in the dunes along the Mayo coast between Clew 

 Bay and Killery Harbour. During the Clare Island Survey this last 

 district was left practically untouched, except by the conchologists, but 

 might yield surprising results if carefully worked. 



If during his researches Canon Bullock-Webster comes in contact 

 with any facts which might throw some light on the conditions under 

 which were deposited the enormous masses of " shell marl " or " chara 

 marl " underlying many of our Irish peat-mosses, those of us who are 

 interested in these deposits would be grateful if he would record these 

 facts in the Irish Xatitralist. Personally I have been led to think that 

 these deposits, which yield an abundant molluscan fauna — though not 

 rich in species — were laid down during a period in which there w^ere 

 exceedingly dry and hot summers and possibly cold winters. The 

 basement layers of some would seem to date from a very early post- 

 glacial period, though deposition may have gone on for long ages. 

 Whether any such marls are forming now is, I fancy, a matter of doubt, 

 though ;Mr. Welch is confidant that such a state of affairs exists in certain 

 favourable localities. Owing to the lowering of the level of some lakes 

 the old deposits of marl are being eroded and re-deposited in deeper 

 water ; therefore, great care should be taken to ascertain that these 

 re-depositions are not mistaken for an original marl in the course of 

 formation. Whether any species of Chara is attractive to any species 

 of mollusk I cannot, unfortunately, say ; but if it were possible for Canon 

 Bullock- Webster to make observations on this subject, some interesting 

 geological points miglit be discovered. It is certain that in the days 

 when marl was in general formation some of the mollusca, now extremely 

 local, were abundant and widespread, e.g., PUinorbis glaber. This may 

 be due to the fact that the conditions w.hich suited the Characeae also 

 were favourable to the snail, but there is the possibility that the presence 

 of the plants may have been desirable, though, of course, not necessary, 

 for the sustenance of the snail. 



May 1 add that I should be very much obliged if any reader of this 

 note would forward to me any samples of this marl which he may come 



