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PRINCIPLES OF STRATIGRAPHY 



deposit is marine rather than eoHan, is at least a surprising fact. 

 Extensive false-bedded limestones composed almost entirely of 

 comminuted marine shells and containing bones of land animals in 

 places occur near Cape Town in South Africa, and belong proba- 

 bly to this type of deposit. (Rogers and Schwartz-43.) Wind- 

 blown calcareous deposits of almost pure foraminiferal shells, and 

 consisting of subglobular Miliolinae and inflated Truncatulina loba- 

 tula, have been found on the Isthmus of Earawalla, between Dog's 

 Bay and Gorteen Bay, on the southwestern coast of Galway, Ire- 

 land. They form low dunes covering an area 1,000 yards from 

 northeast to southwest, and about 350 yards from bay to bay. Land 

 shells occur at intervals, but very few if any marine shells, except 

 such as appear to be derived from kitchen middens in the vicinity, 



Fig. 121. Cross-bedding in Jurrasic oolites of Somersetshire, England. (After 

 De la Beche.) a, a, a, diagonal layers of broken shells, fish-teeth, 

 pieces of wood, and oolite grains, lying in plane of diagonal bed- 

 ding, b, b, b, b, mud layers. 



or have been carried up by birds for food. The surface drift in the 

 North Atlantic, together with local currents, carries an abundance 

 of Foraminifera into Dog's Bay, where every high tide spreads 

 them over the gently sloping strand, together with small Gas- 

 tropoda. They dry rapidly and are carried landward by the wind, 

 the whole surface sometimes being in a state of rolling motion. 

 Foraminifera, Ostracoda, fragments of shells, etc., thus travel 

 across the isthmus, sometimes into the bay on the opposite side. 

 These organisms are not surrounded by an extra coating of lime, 

 as in the case of the Indian examples, probably because such chem- 

 ical deposition of lime is less characteristic of cooler climates. 



Wind-carried Foraminifera have been found in the eastern 

 desert of Egypt, in the sands obtained near the foot of a gully in 

 the hills, about a mile west of the Gulf of Jemsa, on the western 

 side of the Red Sea. On the islands in the Red Sea no siliceous 

 sand is to be found, as a rule. The sands are calcareous, and are 

 chiefly formed from comminuted fragments of corals and shells, as 



