266 Scientific Proceedings, Royal Dublin Society. 



It is possible that the cold conditions indicated by the erratics 

 in the beach may have been continued into the head period, and 

 perhaps intensified. A still further intensification may have 

 resulted in the invasion of the area by land-ice. Again, rapid 

 diurnal alterations of temperature might be produced merely by a 

 change of meteorological conditions without any lowering of 

 mean temperature. This would happen if the supply of moisture 

 were diminished during a portion of the year, and a climate thus 

 established with arid seasons, in which sun-heat by day and 

 radiation by night would be very intense. 



The marly boulder-clay is a greenish or bluish-grey clay, 

 which effervesces freely with acid. Some parts, particularly 

 those of a greenish tinge, exhibit on a surface exposed to the 

 weather, a fine lamination which is frequently contorted. This 

 is well seen in Whiting Bay, east of Youghal. Other parts are 

 compact and sometimes well-jointed. The jointing is very per- 

 fectly developed in the coast sections in the middle of Ballycottin 

 Bay. The marl weathers at the top to a brownish clay, with 

 blue-faced joints. It contains fragments and numerous smaller 

 particles of the shells of marine mollusca, including several 

 northern and Arctic species. 



List op Shells found iet the Majrlt Bouldee-clat. 1 



Ballycroneen Bay. 



Pecten opercularis, Linn. 

 Astarte sulcata, Da Coda. 

 Mytilus, sp. 

 Bucoinum undatum (young). 



Ballycottin Bay. 



Nuculana (Leda) pernula, 0. F. Midler. 



Cyprina Islandica, Linn. 



Mytilus, sp. 



Astarte borealis, Chem. 



Astarte sulcata, Da Costa. 



Mactra solida, Sow. 



Tapes, sp. 



Nucula nucleus, Linn. 



1 We are indebted to Mr. J. de W. Hinch for the identification of the shells. 



