CALCAREOUS ANEMOLITHS 573 



to the sweep of the prevaiHng winds. These dreikanter may then be 

 buried in deposits of eoHan, fiuviatile and even marine origin, but 

 only in the first case are they likely to be left in an undisturbed 

 position. 



besides being found in abundance in desert and semidesert areas 

 of to-day (see ante, Chapter II), they are also known from a 

 number of older deposits. They have been described by Walther. 

 from the pre-Cambric Torridon sandstone of Scotland, and they 

 are not uncommon in the basal Cambric Eophyton sandstone of 

 Sweden. At the other end of the scale they are found in Pleisto- 

 cenic deposits of Germany and North America, where in some 

 cases, as at Cape Cod, Massachusetts, they are buried by subse- 

 quent fluviatile and eolian deposits in the position in which they 

 were formed. (Davis.) They have also been found in the Triassic 

 beds of England, where wind-corraded and polished surfaces, and 

 surfaces showing insolational flaking also occur. 



Accumulations of pebble beds, especially where the pebbles are 

 covered with desert varnish, may in some cases also be traced to 

 extensive eolation, which removed all the finer material and subse- 

 quently buried the residual pebble beds under new accumulations 

 of eolian sands and dust. What seem to be pebbles of this kind 

 buried by dunes of oolites, which have since been changed to iron 

 appear at the base of the Siluric section in Wisconsin. 



Calcareous and Other Nonsiliceous Eolian Sands. 



Recent and Tertiary Examples. On Bermuda, where siliceous 

 material is wanting, the dunes are composed entirely of calcareous 

 material. This consists in part of fragments of shells and in part of 

 coral sand, while foraminiferal shells (Orbiculina, etc.) frequently 

 make up a considerable portion of the deposit. The older dune 

 sand of the islands has been consolidated into a hard rock (anemo- 

 calcarenyte, Bermudaite), which is locally known as "sandstone," 

 though nearly pure calcium carbonate. Shells of Helix and Livona 

 are enclosed in this calcarenyte, the former a land shell, the latter 

 marine. These shells of Livona in some cases were carried into the 

 dune sand by the wind, but in others they were buried, together 

 with Area, Chama and Tellina, by the dunes which advanced over 

 the site on wliich they grew. Below the beds of calcarenyte are 

 finer layers, some of them calcilutytes, and, like the calcarenytes, 

 they generally show wind-drift structure and fine lamination. Eol- 

 ian limestones composed almost wholly of oolite grains are now 



