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CARBONIFEROUS AND PERMIAN FORAMINIFERA. 



§ 3. ZOOLOGICAL CONSIDERATIONS. 



The Rhizopocl-fauna of the Carboniferous and Permian epochs is not without interest 

 in some of its zoological phases. The relation of its various component types to each 

 other will be better discussed when describing the individual genera, but the salient 

 general features by which it may be compared with the corresponding groups of 

 other geological periods, the bearing of ascertained facts upon accepted theories of 

 classification, and other kindred matters, form a subject for separate consideration. 



Four distinct systems have been proposed at different times for the classification of the 

 Foraminifera. That of D'Orbigny in 1S26 had a purely artificial basis' and has now 

 fallen into disuse, whilst that of Professor Max Schultze, published in 1854, has never 

 been extensively adopted. Neither of these need be dwelt upon. 



The schemes of classification worked out independently by Professor Von Reuss in 

 Vienna, and by Dr. Carpenter, Mr. W. K. Parker, and Professor T. Rupert Jones in this 

 country, and published almost simultaneously (i. e. in 1861 and 1862), are alone in use at 

 the present time, 1 and their essential features are practically identical, notwithstanding many 

 differences in detail. Minute criticism would be out of place here, and is the less needed 

 because amongst those who have worked much upon the subject there would be a pretty 

 general agreement in the opinion that the English arrangement is laid down on broader 

 lines, — that in it more importance is attached to the natural relationship of the series of 

 forms traceable to a single type, and less to mere morphological variations ; — whilst that 

 of Professor Von Reuss, with its smaller groups and somewhat more artificial distinc- 

 tions, has considerable advantages in the facilities it affords for the naming and arrange- 

 ment of specimens. But the fact that concerns us at the moment is that in these two- 

 independent systems the basis of their primary divisions is the structure of the shelly 

 investment or test. 



In general terms Foraminifera are divided into the same two classes — those with 

 non-porous or imperforate, and those with porous or perforate tests. The former of 

 these two divisions (" Imperforata ") is in both systems, subdivided into two sections, 

 one including those types which have composite tests, that is, built up of sand-grains, 



1 Since the above was written Prof. T. Rupert Jones's paper on "Variability of Form in Forami- 

 nifera" has been published in the 'Monthly Microscopical Journal' (February 1st, 18/0). It contains 

 a list of genera arranged in smaller groups than the classification formerly proposed by the same author 

 and his colleagues, though accepting the same general basis. It would be an injustice to express an opinion 

 on so short an acquaintance, and the proposed scheme does not materially affect the arrangement of the 

 Carboniferous species. 



