Brackish-water Fi oraminifera. 279 
Some genera of Rhizopoda are regarded as caleareous or 
arenaceous, and proper to the sea (Foraminifera), others as 
chitinous or arenaceous, and pertaining chiefly to fresh water 
(Gromia and Diffugia); the evidence afforded by specimens 
obtained under intermediate (brackish) conditions indicates 
the problem, whether gradual modification of external circum- 
stances, with a large allowance of time, may not be held to 
account for many characters supposed to be of generic or even 
ordinal importance. 
The converse is also tru 
from several additional brackish localities have been collated, 
in order to render the synopsis as comprehensive as circum- 
stances admit. 
Of Group L, pertaining to river-estuaries of England and 
Scotland, the following columns are omitted :—p, Warn Burn; 
1, River Ouse at Goole ; J, River Humber; K, River Deben; 
L, River Stour; m, River Thames; and N, Fowey Harbour. 
Of Groups II. & II., referring to the English Fen-district and 
Holland, the following are wanting :—P, Whittlesea Dyke ; 
X, Ormesby Broad; z, Lake Lothing; cc, River Ouse, Nor- 
folk; re, River Maas. It is to be regretted that the Whittle- 
sea-Dyke gathering has been mislaid, as it contained a pre- 
onderance of Foraminifera. The material from Ormesby 
road contained a considerable number of Diflugiæ, but no 
other Rhizopoda. 
In the Table of Foraminifera the letters heading the columns 
correspond with those used for the same localities in that de- 
voted to the Ostracoda, and the additional columns are referred 
to by numbers (1 to 15). A few brief memoranda concerning 
the localities not previously described are necessary to com- 
plete our lapogiapkical notes. 
„1. River Tay, near Errol —A gathering taken south of 
Errol, between the river and the gamekeeper’s house, in soft 
muddy gullies and lagoons. The shore for a considerable 
