POST-TERTIARY FOSSILIFEROUS DEPOSITS. 7!) 



2. They contain sometimes a mixture of deep-sea and littoral species, evidencing the 

 action of tides and changing currents. 



3. While in many beds the fossils occur in situ, in others they are very much broken 

 and fragmentary. 



4. The proportion of Arctic species varies in different beds. 



IV. Some of the Arctic shell-beds mark coast-lines at varying heights — coast-lines 

 which could not have coexisted. The case of Jordan Hill, Glasgow, has been instanced, 

 where a littoral shell -bed exists sixty-three feet above the sea ; while a similar littoral 

 shell-bed is met with on the low ground north of Paisley at about fifty feet lower 

 level. 



V. The Arctic shell-beds exist at various heights above the sea. On the west of 

 Scotland the beds we have described range from 526 feet at Airdrie (the highest point at 

 which Arctic shells have yet been discovered in Scotland, although there is no reason to 

 conclude that they will not ultimately be found at higher levels) to half-tide-mark, 

 where, in some cases, they dip beneath the sea and are entirely hidden by modern sands 

 and gravels. At present there are blanks to be filled up between 526 feet (Airdrie) and a 

 group of beds between forty feet and sixty feet. Tangy Glen, Campbelton, is 130 feet; 

 and, doubtless, other beds at a corresponding elevation await discovery. 



Between forty feet and sixty feet we have such beds as those at Oakshaw Hill, 

 Paisley, Paisley and Glasgow Canal, Jordan Hill, Stranraer, &c. 



Between twenty feet and forty feet such beds as those at Paisley (lower levels), Loch 

 Lomond, Loch Gilp, Crinan, &c. 



Between ten feet and twenty feet, such beds as those at Greenock, East Tarbert, 

 Dumbarton, &c. 



Between high-tide-mark and ten feet, such beds as those at Kyles of Bute and 

 almost the whole shore of the Erith of Clyde, Fort William, &c. 



On the east of Scotland, Arctic shell-beds have been found at the following heights : 



Auchleuchries, Aberdeenshire (this bed we have not seen, but give 



it on the authority of Mr. Jamieson, loc. cit., ante) . 300 ft. 



Gamrie (the beds of sand and gravel reaching to 300 feet) . 150 



King Edward . . . . 150 to 200 



Errol . ... . . .45 



Belhelve, Aberdeenshire . . . .40 



Montrose . . . . . .40 



Annochie (passing under sea from a few feet over sea-level). 

 Elie (passing under sea from a few feet over sea-level). 



VI. The position of the Mytilus edulis bed is also noteworthy. 



