INTRODUCTION. 
xiii 
It is very necessary therefore to have the local groups of Foraminifera 
before the eye, rather than to have to search here and there for the 
members of those groups. Moreover the general characters, aspect, or 
facies is striking enough to a palaeontologist, although the slightly different 
varietal forms cannot be fairly distinguished by names ; for every individual 
specimen in some such groups might have a separate name. Indeed 
many binomial (generic and specific) terms have been instituted on such 
slight differences, to the inconvenient swelling of lists and disturbance of 
nomenclature. 
It is certainly often difficult to determine if it he advisable to give or 
to retain binomial appellations for certain specimens of Foraminifera. 
For, on the one hand, there may he an apparent distinctness of form; and, 
on the other, many gradations may he recognizable between what appear at 
first sight to he well-marked varieties or even seemingly distinct species. 
Thus it is often necessary to refer only to the name of the best-known or 
the typical species or notable variety, the type being usually founded 
on that member of the group which shows a good medium development. 
AYhere this plan is followed on a good zoological basis, to avoid multiplica- 
tion of names, an examination of a local group of Foraminifera leads more- 
satisfactorily to a recognition of its peculiar facies and special value, than 
a list of names, which point to differences rather than to consanguinity, 
with slight modifications of a few types. 
For the above reasons, it has been thought advisable to group the Fossil 
Foraminifera in this Catalogue according to their local occurrence and 
geological age— the latter indicating the succession of forms, with or 
without modifications, from one age of the world to another, and the 
former supplying at one view what has been collected from the different 
fossil faunce at places easily recognized. 
At the same time, to enable the student to form some idea of the range 
of the several Foraminiferal groups in time, the following Table, somewhat 
modified from one published in the ‘ Proceedings of the Geologists’ 
Association,’ vol. ii. (1872), p. 181, gives a general view of the occurrence 
and succession of the most important genera from the Silurian epoch to 
present times. 
No columns are here given for the Geological Systems older than the 
Silurian, namely the Cambrian , Precambrian, and Laurentian , because 
only one Foraminifer has as yet been definitely determined among their 
fossils, namely Eozoon, in the Lower-Laurentian marble of Canada, 
although other probable Phizopodal forms have been observed. 
