Frof. Harkness — On the Middle Pleistocene Deposits. 547 



agricultural purposes. Beds of sand are often found associated with 

 the shelly marls; and in the neighbourhood of Preston in Lan- 

 cashire where the shell-bearing strata are seen, they are described 

 by Sir Eoderick Murchison as consisting of porous loose gravel.' 

 Mr. Binney has also described the shell-bearing strata associated 

 with Boulder-clays, as these occur on the Lancashire coast, in the 

 neighbourhood of Blackpool.^ He mentions the association of flint- 

 pebbles with these strata, and he gives a list of the shells, there 

 being eleven forms of univalves, and eight forms of bivalves apper- 

 taining to species, all of which are found in the adjoining sea. 



In the north-east of Scotland there are, in many spots, strata 

 which seem to have a great affinity to the shell-bearing sands and 

 gravels of Ireland, and to those of opposite districts of England and 

 Wales. Before, however, we can determine the exact position of these 

 Scottish beds, it will be necessary to know somewhat more about 

 them. On the southern side of the Moray Firth, some of these 

 deposits occur, and they have been described by Mr. Jamieson.' 



In some cases the Aberdeenshire sands and gravels appear to be 

 very nearly allied to the " Manure gravels " of the County of Wex- 

 ford in their contour, for they occur in the parishes of Cruden and 

 Slains in the form of mounds. They consist of water- worn pebbles, 

 gravels, and sands, with broken shells, among which are fragments of 

 Cyprina Islandica, the form most common in the sands and gravels 

 near Carrick-mines, on the south side of Dublin Bay. These sands 

 and gravels of Aberdeenshire have in some instances large erratic 

 blocks resting on them, and sometimes a red clay hides them from 

 view. 



Strata of the same character as those of Aberdeenshire have been 

 described by Mr. Prestwich as occurring on the south side of the 

 Moray Firth, near Gamrie.* A section of these strata is seen on 

 the coast ; and Mr. Prestwich observes that flint-pebbles are found 

 abundantly on the beach, which seem to have been derived probably 

 from the upper beds of sand and gravel which here also afibrd 

 shells ; the species of Molluscs which occur in these sands and 

 gTavels, like those from the deposits of Lancashire and Cheshire, 

 are not of a peculiarly Arctic type. 



The county of Caithness, in the neighbourhood of Wick, appears 

 likewise to furnish beds having the same position as those on the 

 south side of the Moray Firth. Shells have also been collected from 

 these strata by Mr. Peach.^ Among tlie pebbles which enter into 

 the composition of the shell-bearing deposits of Caithness, Mr. Peach 

 mentions the occurrence of chalk flints as not uncommon. 



The shells from these Caithness beds have been determined by Mr. 

 Gwyn Jefi'reys ; and although they contain a few Arctic types, they 

 are, on the whole, forms which have a wide geographical distribution. 



* Silurian System, page 534. 



2 Mem. of the Lit. and Phil. Society of Manchester. Vol. x. page 121, et seq. 



3 Quart. Journal of the (Jeological Society 18.')8, page 623. 



* Trans, of the Geol. Soc. Vol v., p. 147. New series. 

 6 Brit. Association Eeports, 1862, 1864, and 1S66. 



