24 EHIZOPODA. 



this purpose from suitable localities, or picked, 

 with the aid of a lens, from the fronds of living 

 sea weeds, over the sm'face of which they may be 

 observed to crawl by means of then* pseudopodia. 



12. Distribution of F«ra?5ii«irera in tini<». 



— Eemains of Foramlnifera have been proved to 

 exist in most of the stratified rocks, from the 

 Silurian to the Tertiary inclusive ; many of the 

 forms found in the older formations being nearly, 

 if not absolutely, identical with those which occur 

 in the seas of our own epoch. But the insufficient 

 and superficial manner in which the " genera " and 

 " species " of these animals have too frequently 

 been characterised, has considerably deducted from 

 the value of those facts from which conclusions 

 miofht otherwise be deduced with reference to their 

 distribution. 



Amonof Paleozoic strata remains of these ani- 

 mals have been found to occur in both the Silurian 

 and Carboniferous series. The green grains which 

 lie scattered through the Lower Silurian sand- 

 stones of the neighbourhood of St. Petersburg!! 

 have been shown by Ehrenberg to contain in their 

 interior siliceous casts of Foraminiferous shells, 

 some of which are referrible to such existing forms 

 as Guttulina, Rotalia, and Textularia. The two 

 last mentioned of these have been likewise de- 

 tected in the Carboniferous limestone, certain beds 

 of which, found in Russia and the United States, 

 are composed, for the most part, of the shells of 

 Fusulina, a form which would seem to be exclu- 

 sively confined to this deposit. 



Among secondary rocks, Foraminifera prevail 

 in both the oolite and chalk, being, however, more 



