Structure of Rhizopod Shells. 315 



when we turn to the Palajozoic 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." (Stamme 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 into account all the conditions which come under 

 consideration. In this way we get a phylogeny which agrees 

 better with both the morphological and the palseontological 

 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. These 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 Astrorhizidse, 

 the common stock-form of all the four stems. On the irregu- 

 larly agglutinant Astrorhizidee 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 



