Prof. Harkness — On the Middle Pleistocene Deposits. 545 



dition. These shell-bearing beds, with flint pebbles, rest upon a 

 mass of Boulder-clay containing abundance of striated blocks, well 

 seen at Balscaddan Bay ; and this Boulder-clay reposes immediately 

 upon the Carboniferous limestone. 



The position of the shell-bearing beds, with flint pebbles, at 

 Howth, resting on Boulder-clay, would at first sight appear to indicate 

 a different and a higher horizon for these strata than for beds having 

 the same nature in the Co. of Wexford, since the latter have Boulder- 

 clay above them. 



It must, however, be remembered that, in the Wexford area, the 

 strata upon which the " Manure gravels " rest are not seen. 



On following the gravels and sands of Howth, eastwards, they are 

 found to be covered by Boulder-clay, which does not exceed more 

 than three feet in thickness ; and this Boulder-clay most probably 

 represents the lower portion of the similar deposits which, in Castle 

 Ellis, in the Co. of Wexford, covers the " Manure gravels." 



Subsequently to the observations of Dr. Scouler on the shelly 

 gravels and sands of Howth, Dr. Oldham has described beds of the 

 same nature which occur in other parts of Ireland.^ He also notices 

 the appearance of flint pebbles in these strata ; and he adds to Dr. 

 Scouler's list of shells the following species: — Ostrea edulis, from. 

 Killiney and Bray ; Tellina solidula, not uncommon ; Pecten opercu- 

 laris, from Killiney ; Pullastra decussata, from Killiney and Bray ; 

 Nucula ohlonga, Astarte Gairensis, from Killiney, Bray, and Sugarloaf ; 

 Nucula nucleus ? and Saxicava rugosa, rare. Further observations 

 in these beds also induced him to add to his previous list the fol- 

 lowing forms as occurring near Dublin : — Bostellaria pespelicani, 

 Fusus antiquus, Buccinum undatum, Nassa incrassata, Natica Alderi, 

 Littorina neritoides, Trochus umhilicatus, T. ziziphinus, Triquetra species 

 of Spirolis sp., Balanus (impressions of ).^ 



Since the observations of Dr. Oldham were made on these deposits, 

 as they are seen in the districts around Dublin, they have attracted 

 the notice of the Rev. Maxwell Close, who has paid special attention 

 to the Glacial phenomena of Ireland. The Eev. Mr. Close has re- 

 cognized the occurrence of the shell-bearing sands and gravels in 

 the high ground to the south of Carrickmine's station, on the Dublin 

 and Bray railway. 



Here flint pebbles also make their appearance, and shelly frag- 

 ments, the most abimdant being portions of Cyprina Islandica. 



The Rev. Mr. Close has also detected these shelly sands and 

 gravels on the south side of the Three Rock Mountain, at an eleva- 

 tion of about 1,200 feet above the sea level. 



The several species of mollusca, which have been obtained from 

 the sands and gravels in the neighbourhood of Dublin, are such as 

 are most common in the " Manure gravels " of the Co. of Wexford ; 

 and, like them, they do not indicate Arctic conditions in the seas in 

 which they lived. 



Sands and gravels of a nature similar to those of the neighbour- 

 hood of Dublin and the Co. of Wexford, have been found in other 



1 Op. Cit., supra, Vol. III., p. 61. 2 Qp. Cit. supra, Vol. III., p. 131. 



VOL. VI. — NO. LXVI. 35 



