CORRESPONDENCE. 309 
could not greatly assist zoological investigation. Some interesting 
conclusions, however, were arrived at, valuable and true in the main,— 
namely, that the same kinds of Foraminifera occur both recent and 
fossil ; that, nevertheless, each set of strata has more or less decidedly 
its own special group of Microzoa ; and that Chalk in particular, and 
probably most limestones and calcareous marls, are largely composed 
of Foraminifera (Polythalamia, Ehrenb.). Thus these minute or- 
ganisms, with Coccoliths (Morpholites, Ehrenb., in part), appear to be 
the main constituents of the White Chalk. Although even recent forms 
of Microzoa are found in the Chalk, Ehrenberg warns us that these 
lowly creatures only go to prove that this, like many other calcareous 
rocks, is a “ Halibiolith,’ or marine deposit of organic origin; and 
not that the Cretaceous and Recent periods have been closely linked 
by identity and continuity of high grades of life.* 
Amplifying with his own increased knowledge the already published 
observations on the persistence of low orders of life, Dr. Ehrenberg, 
having studied some living Foraminifera of the North Sea, at Cuxhaven, 
contributed in 1839 an interesting memoir to the Berlin Academy, 
figuring two living species (Polystomella striato-punctata and Nonionina 
umbilicata) with great exactness, as well as some obscure forms, which 
he found in both the living and the fossil state} This memoir is 
given in English, with the original plates, in Taylor’s ‘Scientific 
Memoirs,’ vol. iii., art. xiii. 
In 1843 several highly magnified figures of minute recent Forami- 
nifera from America were treated of and illustrated by Ehrenberg in 
the Berlin Academy Transactions for 1841. 
Dr. Ehrenberg’s memoir “ On the muddy deposits at the mouths and 
deltas of various rivers in Northern Europe, and the Animalcules found 
in these deposits” { was noticed at large in the ‘ Quart. Journ. Geol. 
Soe.’ vol. i. p. 251, &c., as illustrative of the influence of microscopic 
life (chiefly Diatomacez) on recent and fossil stratified accumulations. 
Few can now recollect the astonishment with which geologists received 
in 1836 the assertion that large masses of rock, and even whole strata, 
are composed of the remains of microscopic animals and plants ;§ but 
this assertion has been confirmed and extended, largely by Ehrenberg’s 
further labours, and we now recognize many “ Halibiolithic” deposits 
and Diatomaceous earths. 
In the ‘ Abhandl. Berlin Akad.’ for 1847, many extremely minute 
Foraminifera, occurring in wind-dust on different occasions, in several 
parts of Europe, are described and figured. They form part of the 
curious gatherings of invisible things that wind-storms make and dis- 
perse in their whirlings over the surface of the earth,—sweeping the 
sea-shore, sand-bank, and dry river-bed, the volcano, the desert, and 
* ¢ Quart. Journ. Geol. Soc.’ vol. xxviii. pp. 122-124. 
+ The late Mr. Thomas Weaver, F.R.S., in the ‘ Annals and Mag. Nat. Hist.’ 
1841, and in the ‘ Philos. Mag.’ of the same year, gave a full abstract of two of 
Ehrenberg’s memoirs (read in 1838 and 1840) above mentioned, together with an 
appendix touching the researches of Alcide d’Orbigny on the Foraminifera of the 
Chalk of Paris. 
t From the ‘ Abhandl. k. preuss. Akad. Wissenschaft. Berlin’ for 1843. 
§ ‘Proceed. Geol. Soc.’ vol. iii. p. 62. 
