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THE FOSSILIFEKOUS DEPOSITS

of the higher latitudes : and it is a curious fact, that in theGamrie and Castleton deposits we find it of a considerablygreater size than anywhere else in Scotland . My largest spe-cimens from the Clyde beds hardly exceed an inch in length;whereas my largest Gamrie specimens are nearly two incheslong, and their breadth very considerably exceeds the lengthgiven as British by Professor Forbes.

Most of the boulder clays,—especially the higher lyingdeposits,—I regard as more modem than these Banffshire beds. They mark a period when the land sat low in thewater, and existed as but a group of wintry islands. To thesouth of the Grampians , their organisms are but few; theyhave yielded at wide intervals horns of the rein-deer, andtusks of the northern elephant; but, save in an insulatedpatch in Wigtownshire, no shells. The boulder clay in Caith-ness is, on the other hand, rich in shells. They excited theattention of a mineral surveyor, who flourished about the be-ginning of the present century,—old John Busby,—more thanfifty years ago ] they also attracted the notice of the late Sir John Sinclair ; and in one of my Caithness journeys, I wastold by my friend Mr Dick, that one of the hills on whichthey occur has borne from a still more early period the nameof “ Buckie's Hillbut to Mr Dick himself, and to Mr Cleg-horn of Wick, has the working out of the deposit been mainlyleft. And so effectively has it been done, that Mr Dick, ashe informs me, has not for a considerable time past succeededin finding in it a single new shell. The prevailing molluscsof the deposit are Gyprina Islandica and Turritella communis,especially the former; the prevailing Astarte , though the Arc-tica also occurs, is Astarte elliplica; the prevailing Tellina,Tellina Solidula. Tellina proxima is of smaller size than inthe Gamrie beds ; and Natica clausa less common. Still thedeposit is very decidedly a boreal one in its shells, and in itsmechanical phenomena the most decidedly boreal of the group.