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GEOLOGICAL DISTRIBUTION OF FORAMINIFERA. 369 
_ of marl full of particles of greensand. These have evidently 
_ been washed out of the preceding cretaceous beds of firestone 
or glauconite ; and re-deposited in the chalk strata in which 
Biay are now en ao 
Along the sea-shore,.to.the east of. Brighton, there is a 
bank of sand and calcareous mud, the detritus of the neigh- 
bouring cliffs, in the progress of formation; and in this 
sediment Mr. Reginald Mantell discovered recent Rotaliee, 
Nodosariz, &c., with frustules of Bacillariz, Coscinodisci, 
Naviculz, and other diatomaceze ; associated with creta- 
ceous polythalamia washed out of the chalk.t The difference 
in the aspect of the recent and fossil organisms was so 
evident, as to leave no doubt of the correctness of this inter- 
pretation. Here, then, at the present moment, a deposit is 
going on, whose organic contents consist of an assemblage of 
species of living animalcules of our seas, with the fossil 
forms of the ancient chalk ocean ; in like manner as in the 
bed of the Nile, the Nummulites of the tertiary rocks are 
being imbedded with the existing mollusks and desmidieze of 
that river (ante, p. 345). 
GEOLOGICAL DISTRIBUTION OF THE FoRAMINIFERA.—Accord- 
ing to the observations of M. D’Orbigny, the first appearance 
of the tribes of minute beings which have played so impor- 
tant a part in the elaboration of materials for the formation 
of the sedimentary rocks of the secondary and tertiary 
ages, and are at this moment invisible but powerful agents 
in the accumulation of calcareous sediments at the bottom 
of the sea, was in the Carboniferous epoch, and by a single 
type, the Fusulina (ante, p. 346). I believe no certain 
evidence of the occurrence of Foraminifera in Silurian or 
Devonian deposits has been obtained. 
M. D’Orbigny gives the following summary of the distri- 
bution of the known fossil and recent species :— 
* M. D’Orbigny. t See ante, p. 99. 
VOL. I. BB 
