I92I. VLmcn—Post-Glacial Climatic Optimum in Ireland. 93 



These western Scandinavian marine deposits of the 

 Littorina Sea have been named Tapes beds and divided in 

 two groups. The Older Tapes strata are characterized by 

 the presence of Tapes decussatus and T. aureus, Ostrea edulis, 

 and other species, and are considered to coincide with the 

 period of maximum depression of the land, and also to 

 coincide with the greatest temperature reached in post-Glacial 

 times, the climate during this period being a temperate 

 maritime one with the Oak as the predominent forest tree. 

 The Younger Tapes strata (the Dosinia beds) have Dosinia 

 {Venus) exoleta, Tapes edulis ( Tapes virgineus of Jeffreys), 

 Lutraria elliptica and Psammobia vespertina as characteristic 

 mollusca and a climate not quite so warm as in the Older 

 Tapes period, and with the Beech becoming predominent 

 in the woodlands. 



As regards the position of the Tapes beds in the human 

 history of Europe we can say that the Tapes fauna has been 

 found in the kitchen-middens, a fact which would indicate 

 the general contemporaneity of the Tapes fauna and 

 Neolithic man, while the Younger Tapes or Dosinia beds 

 are considered to have accumulated in the Bronze Age. 

 Another point of interest, and one to which we will return 

 when we come to deal with the Estuarine Clays of Ireland 

 is the great exuberance of the fossil mollusca of the Tapes 

 beds ; every writer on the subject pointing out the great 

 abundance and large size of the shells, and this exuberance 

 of life in the Tapes period is the more remarkable when we 

 remember that Tapes decussatus, Tapes aureus, Dosinia 

 exoleta, Tapes edulis, Lutraria elliptica and Psammobia 

 vespertina have since disappeared from Denmark, while the 

 Oyster, one of the most noted of the Tapes fauna for its 

 great size and immense numbers, is now very restricted 

 in its distribution around the Danish coast. 



The latest marine deposits to be recognised in Scandi- 

 navia are the Mya beds, in which My a arenaria is the domi- 

 nant species, with the genus Tapes only represented by 

 Tapes pullastra. The climate was a temperate insular one, 

 with the Beech as the most important woodland tree, and 



