A. EARLAND ON FORAMINIFERA. 407 



It is, however, of great importance, owing to the fact that these 

 few forms constitute a large proportion of the " Plankton " 

 surface life of the ocean. They swarm in infinite numbers at or 

 near the sea surface, forming a staple food supply for the higher 

 forms of life ; and their dead shells, falling in an incessant rain 

 to the sea bottom, are there building up those deep-sea deposits 

 which have of late years attracted so much attention. Some 

 idea of their enormous numbers can be gathered from the fact 

 that their dead shells form as much as 80 per cent, of some 

 specimens of Globigerina ooze (the average in 118 specimens of 

 Globigerina ooze examined by the Challenger expedition being 

 53*10 per cent.), and that it is estimated that the deposits of 

 Globigerina ooze alone have an area of over forty-nine million 

 square miles, while their thickness cannot even be conjectured, as 

 the process has probably been in operation for several geological 

 epochs. They are seldom found in any numbers in the neigh- 

 bourhood of land in these latitudes, and are consequently of rare 

 occurrence in our shore gatherings. 



The second or non-Pelagic group contains all the remaining 

 Foraminifera, or 99 per cent, of the known species, and includes 

 the whole of the Porcellaneous and Arenaceous subdivisions 

 which are entirely unrepresented in the Pelagic group. They 

 are all, normally, inhabitants of the sea bottom, having little 

 power of motion ; and, although some of the species have an 

 almost universal range both in latitude and depth of water, they 

 are, as a rule, confined to particular zones of temperature and 

 depth. In dealing with shore gatherings we shall be most con- 

 cerned with those species which flourish in and immediately 

 below the " littoral " zone, and I will now try and explain how 

 their shells are to be found between tide marks. The majority 

 of the tests are those of dead foraminifera. When the sarcode 

 body dies it decomposes, and the chambered tests, filled with the 

 gases of decomposition, rise, and drift with the currents until 

 they come ashore. Being lighter than the sand, they take longer 

 to settle after the wave has retreated, and are consequently 

 retained in the troughs or ripple marks in the sand, where they 

 can be detected with the naked eye as faint white lines on the 

 sand, running parallel with the retreating tide, or in white 

 patches of greater or less extent when the shells have been 

 caught in an eddy. The prominence of these markings depends. 



