FORAMINIFERA OF THE FENS. 367 
which contain foraminifera in abundance, are so numerous, 
that it is unnecessary to particularize any. The sands of 
the Paris basin in some localities are so full of microscopic 
_ forms, that a cubic inch of the mass contains sixty thousand. 
_ The friable calcareous strata at Grignon are a loose aggregate 
of the shells of foraminifera and minute mollusks ; and as 
the fossil shells from that locality are very common, and 
- generally filled with débris, the student will have no ditheulty 
_ in obtaining specimens for examination. The tertiary argil- 
 laceous deposits of England are less rich in foraminifera than 
_ the arenaceous ; but the usual types occur in the London 
- Clay, at Highgate, Clapham Common, Bracklesham Bay, &c. 
The Eocene marls of the United States are rich in forami- 
 nifera. 
FoRAMINIFERA OF THE FENS oF LINCOLNSHIRE AND CAM- 
_ BRIDGESHIRE.—Though the alluvial deposits of the fen- 
districts are comparatively of modern date, yet the rich 
assemblage of foraminifera contained in the clay of certain 
districts is so interesting and instructive, that a brief notice 
of them must not be omitted. The foraminiferous character 
of the Lincolnshire alluvium was first made known to me by 
specimens from Bolton, sent me by Professor Williamson ; 
and their extension over a wide area in Cambridgeshire, by 
a liberal supply from Mr. Smith, of March. The bed that 
abounds in these shells, is about seven feet beneath the 
surface, and consists of a fine sea sand combined with carbo- 
naceous and argillaceous matter. By washing about a 
gallon of this earth in water, an ounce of polythalamia and 
organic detritus may be obtained. The perfect shells are as : 
fresh as if just dredged up from the sea ; the soft parts—the 
membranous segments held together by their tubular con- 
nexion—in many instances remaining in the shell; these 
parts may be obtained by the solution of the shell in acid. 
When the Rotaliz are rendered transparent by immersion 
in Canada balsam, their appearance by transmitted light is 
Bees 
