544 Frof. Harkness — On the Middle Pleistocene Deposits. 



univalves are also found in the gravels, some of which are in a perfect 

 state. 



In the neighbourhood of the town of Wexford, and to the south 

 thereof, the same deposits make their appearance ; but here, as else- 

 where, the strata on which they repose are not seen, and here they 

 have no Boulder-clay above them. 



Of the species of shells determined by the late Prof. E. Forbes from 

 the "Manure gravels" of the Co. of Wexford, forty -three are common 

 British forms, amongst which is Fusus antiquus, the variety contra- 

 rius being abundant among the specimens in the collection of the 

 Irish G-eological Survey. The specimens of this form, collected by 

 myself from Castle Ellis, were of the ordinary variety and of small 

 size. Nine of the species from the " Manure gravels" are forms 

 which now occur in the northern British Seas ; seven appertain to 

 Boreal America, or to the coast of Greenland ; and four are now 

 found in seas south of the British Isles. Taking the whole of the 

 shells, they appear to indicate a temperature somewhat colder than 

 that which prevails in the present sea of the Wexford coast, but by 

 no means such a rigorous climate as is represented by the shells 

 which have been obtained from the deposits of Scotland and else- 

 where reposing upon the Boulder-clays. 



The occurrence of Boulder-clays above the shell-bearing sands and 

 gravels of the Co. of Wexford, would, at first sight, induce the con- 

 clusion that these strata appertain to a horizon nearly allied to that 

 of the Norwich Crag ; and this inference is, to some extent, prevalent 

 concerning them. 



It is, however, necessary to look for their equivalents elsewhere, 

 and to see the conditions under which those equivalents present 

 themselves, before arriving at any conclusion as to the age and 

 position of the " Manure gravels." There are two features in con- 

 nection with these " Manure gravels" of the Co. of Wexford which 

 are highly characteristic of them : one is, the presence of shells, and 

 fragments of shells, which distinguishes them from Eskers, to which 

 they are nearly allied in arrangement and in the general nature of 

 their contents ; the other feature which marks them is the constant 

 occurrence in them of flint pebbles, which are almost altogether 

 absent from the Eskers. 



There are several localities in Ireland where beds, having the 

 same nature and affording precisely the same contents as the 

 " Manure gravels " of the Co. Wexford, are to be found. 



One of these localities is the north side of the headland of Howth, 

 the northern boundary of Dublin Bay. The strata, which are here 

 well seen near the village of Howth, have been described many 

 years ago by Dr. Scouler.^ They consist of sands and gravels, the 

 latter being limestone fragments, with which are associated flint 

 pebbles. The section is about 200 feet in thickness ; and Dr. Scouler 

 states that the beds afford Turritella terebra, Turbo liitoreus, Nerita 

 littoralis, Buccinum undatum, Cardium edule, Cyprina Islandica, 

 Pecten varius, and Dentalium. entale, generally in a fragmentary con- 

 1 Dublin Geological Journal, Vol. J., p. 270. 



