288 THE FORAMINIFEEA 



These deposits of Coral Mud and Sand only differ 

 from one another in the former containing a larger 

 percentage of fine amorphous matter, chiefly car- 

 bonate of lime, whilst the coral sand, occurring 

 generally at less depths, consists of organic particles, 

 with a small or almost inappreciable quantity of fine 

 material. 



The Coral Sands, forming on the slopes and shoals 

 of the reef, are sorted and sifted by wave action, and 

 consolidated sometimes by the deposition of calcareous 

 cement, or by the growth of Lithothamnion and 

 encrusting Foraminifera ; the latter often covering 

 patches of the sand measuring as much as five 

 inches across, and due to the continuous growth of 

 one particular organism — the remarkable Folytrema 

 plan Kin of Carter. 



The proportion of the Coral Sand actually due to 

 the remains of corals is usually very small, and there- 

 fore the term must be regarded as indicative of 

 association rather than of composition. 



The foraminiferal fauna of the Coral Sands 

 presents many features of interest, and the assem- 

 blages formed under the conditions associated with 

 reef-building organisms often have a distinct character 

 by themselves. We may find under favourable and 

 variable conditions, such as these, an extensive series 

 of foraminiferal forms, many of the shells being of 

 great delicacy and beauty. 



One of the most remarkable foraminiferal 

 deposits of Coral Sand was dredged from Eaine's 

 Islet, Torres Strait, at 155 fathoms, by the 



