Structure of Rhizopod Shells. 315 
when we turn to the Paleozoic formations, and especially the 
Carboniferous, which here alone has furnished a rich Forami- 
niferan fauna.... In another phenomenon we find a further 
confirmation of the opinion that the calcareous Foraminifera 
have been developed from the arenaceous forms. It has already 
been mentioned that in both divisions there often occur parallel 
forms which show a great similarity to one another in their 
whole conformation ; but on closer examination, at least in a 
number of groups, the circumstance that the differentiation 
and individuality of the different types are much less in the 
arenaceous than in the calcareous series becomes exceedingly 
striking . . . Moreover, when we can trace the same types 
in the two divisions the characters appear much more dis- 
tinctly and clearly in the calcareous forms ; although transi- 
tions are present, the different types do not melt into each 
other so completely as in the arenaceous forms, and the 
multiplicity is much greater than in the latter.” (Stiimme des 
Thierreichs, pp. 168-169.) 
This most recent conception of the natural system or phylo- 
geny of the Thalamophora is decidedly to be characterized as 
a very happy idea, and deserves to be greatly preferred to 
the various attempts previously made at a natural grouping 
of the Thalamophora. A special advantage of Neumayr’s 
theory is to be found in the fact that it does not lay the 
principal stress upon any single character selected more or 
less arbitrarily, such as the perforate or imperforate constitu- 
tion of the shell, the shell-material, or the number and 
arrangement of the chambers, which fault, as the author 
justly points out, affects all previously established so-called 
natural arrangements of the Thalamophora; but it takes 
equally imto account all the conditions which come under 
consideration. In this way we get a phylogeny which agrees 
better with both the morphological and the paleontological 
facts than is the case with the older systems. In accordance 
therewith the Thalamophora are divided up into a great 
number of more definitely limited groups, which, on the 
whole, agree with those established by Brady. ‘hese are 
distributed upon a small number (four) of great stems, which 
run parallel and independently side by side, and are connected 
only at the root by the primitive agglutinating Astrorhizide, 
the common stock-form of all the four stems. On the irregu- 
larly agglutinant Astrorhizide follow the regularly agglutinant 
forms, the simplest of which directly approach the com- 
mon stock-group, while the more highly developed forms 
already take on a divergent direction and become distributed 
over the four main-stems established by Neumayr ; with them 
