1 62 August, 



NAJAS MARINA IN THE MEGACEROS-MARL OF 



LOUGH GUR. 



BY CLKMENT REID, F.R.S. 



So little is 3'et known about the Prehistoric and newer Ter- 

 tiary flora of Ireland, that the discovery of Najas marina may 

 encourage botanists to take up the subject. Dr. Scharff a few 

 weeks ago sent me three small samples of peat, marl, and sand, 

 from excavations made at Lough Gur in order to obtain 

 Hfcgaceros. The samples were too small to 5'ield man}- species ; 

 but the)^ showed that here, as at other spots, the marl}' deposit 

 is largely a O^ra-marl, yielding also freshwater shells, leaves 

 of sallow {Salix cincrca), and a few seeds of common bog 

 plants. One fruit only of Najas viarhia was also found. 



Najas marijia is a submerged flowering plant which, in 

 Britain, onl)- lives at a single spot, in Hickling Broad in Nor- 

 folk. Its former distribution, however, was much wider. It 

 occurs at several localities in Norfolk and Suffolk in the Pre- 

 glacial '"'Cromer Forest-bed" ; it is found in a newer deposit 

 (probabl}^ Interglacial) at Hitchin, in Hertfordshire; it also 

 occurs in Barry Docks, in South Wales, in a marl associated 

 with a submerged peat, in which was discovered a polished 

 stone implement. The marl at Barry Docks may be of the 

 same date as the Megaceros-r^2x\'6 of Ireland. 



From Ireland Najas marina has not been recorded previousl)^; 

 but the distribution of the species of this genus is singularly 

 sporadic in both living and fossil state. Njlexilis, still living 

 in Ireland, has not yet been found fossil in Britain, though it 

 occurs both recent and fossil at several places in Scandinavia 

 and German3^ N. gramiiiea^ a widely distributed tropical 

 species, lives in Britain as an accidental introduction into a 

 canal w^hich receives waste hot water from a mill. N, viiiiory 

 a plant of the Mediterranean region and of central Europe, is 

 found in Britain in Preglacial and Interglacial beds. 



Geological Survey, London. 



