94 



The Irish Naturalist, 



August, 



the archeological date of the Mya deposits may be regarded 

 as occurring in the Iron Age.^ 



The general succession of the post-Glacial deposits in 

 north-east of Ireland may be described in descending order 

 as follows : — 



Mya beds, 



Raised Beaches ^ ^ ^ 



T-i. • /T ^ XT- X • n^ > Contemporaneous 



Inracia (Later) listuarme Clays J ^ 



Scrobicularia (Older) Estuarine Clay, 



Submerged Peat, 



Glacial and late-Glacial sands, gravels and clay, 

 Boulder-clays. 



The Boulder-clay and the late-Glacial deposits call for 

 no special comment here. The Submerged Peat is much 

 compressed, and is full of trunks and boughs of Willow, 

 Hazel, Alder and Pine, and contains also the remains of 

 the Wild Boar and Red Deer, and all the evidence points 

 to the vegetation which forms the peat having lived on 

 the spot where it is now found. 



The Scrobicularia (Older) Estuarine Clay is a somewhat 

 sandy littoral clay, characterized by the roots and leaves 

 of the Grass-wrack [Zostera marina) and containing immense 

 numbers of those mollusca which live between tide-marks. 

 Among these may be mentioned Mytilus edulis, Cardium 

 edule, Tapes decussatus, Tellina halthica, Scrobicularia 

 piperata, Hydrohia ulvae. 



The Thracia (Later) Estuarine Clay is a fine tenacious 

 deposit characterized by such Mollusca belonging to the 

 Laminarian or Coralline zone, as Montacuta bidentata, 

 Cardium echinatum, Lucinopsis undata, Scrobicularia alba, 

 Thracia convexa, Turritella terebra. 



The Raised Beaches are considered to be contemporaneous 

 with the Thracia or later Estuarine Clay, and in many cases 

 should be regarded as portions of the sea bed which have 

 been deposited on the surface of the Scrobicularia (Older) 

 Estuarine Clays. 



ly. Nordmann : Post-glacial climatic changes in Denmark, see pp.3 13- 

 328, Die Veranderungen des Klimas, 1910. 



V. Nordmann : On remains of Reindeer and Beaver .... in 

 Denmark, Danmarks geologiske Undersgelse II. Rackke, Nr. 28, 1915. 



