CALCAREOUS OOZES 



455 



shells of littoral species may be washed up onto the shore, where 

 they form an extensive foraminiferal sand, as in the case of the 

 Orbiculina shells of the Bahamas. These shells may then be blown 

 inland to form beds of foraminiferal limestone often of great purity, 

 at a distance from the shore on the dry land. Such is the case 

 with the limestone of Junagarh on the Kathiawar peninsula, West 

 India (see Chapter XIII), and the foraminiferal limestones of 

 Jamaica may have a similar history. 



Zoogenic oolites. Among the numerous theories advanced to 

 explain the origin of the oolites is that of their zoogenic origin, the 

 role of oolite-former being commonly assigned to Foraminifera. 

 Thus Ehrenberg regarded the oolites of the Jura of many locali- 

 ties as formed by the more or less recrystallized shells of Melonites 



Fig. 107. Pteropod ooze, x 10. (After Murray and Renard.) 



(Mikrogeologie). The oolite-forming organism described by 

 Bornemann as Siphoncma incrustans and referred to alg?e was 

 relegated by Nicholson to the Foraminifera on account of its re- 

 semblance to the recent foraminiferan S\iringamnina fragilissima 

 Brady, while Sorby and Withered also regard it as a foraminiferan, 

 the former finding its resemblance closest to Hyperaninina vagans 

 Brady. This organism forms oolites in the Siluric and Devonic. 

 The oolites of the Muschelkalk regarded by Bornemann as due to 

 algous growths are referred by Frantzen to zoogenic origin, as lime 

 separated by acid of the animal organisms. By others these same 

 oolites have been regarded as of purely hydrogenic origin. 



Recent Pteropod Ooze. (Fig. 107.) This is found in only a few 

 tropical and subtropical regions resting like the foraminiferal oozes 

 upon the swells and submarine ridges. In all there are known 6 



