18 CARBONIFEROUS AND PERMIAN FORAMINIFERA. 



into which the Foraminifera have been divided, but rather to intermediate types, which 

 are neither invariably arenaceous nor uniformly perforate in their shell-texture. 2nd. That 

 in the modifications of these primitive intermediate types some varieties occur which are 

 conspicuously sandy and imperforate, others that are essentially hyaline and porous ; and 

 there arc not wanting indications that their varietal peculiarities have been transmitted as 

 permanent characters, thereby becoming the origin of the two parallel isomorphic series. 

 3rd. From negative evidence that the porcellanous imperforate group (MILIOLIDA) is of 

 later creation. 4th. That the Permian llhizopod-Fauna is very limited as compared with 

 the Carboniferous, being confined to five generic types (Trochammina, Nodosinella, 

 Nodosaria, Textularia, and Fusulina), representing, however, at least four distinct families 

 of Foraminifera. 



4. HISTORY. 



It would be profitless labour to attempt now to determine at what period the idea 

 first gained credence that portions of the earth's crust were largely made up of the 

 remains of minute testaceous animals ; but that the fact was recognised in its full signifi- 

 cance before the end of the last century, and in a measure understood, the beautiful folio 

 volumes of the Abbe Soldani abundantly testify. The pateontological sections of 

 Soldani's " Testaceographia " relate chiefly to the Sub-Appenine clays of Tuscany ; but 

 other observers followed, Fichtel and von Moll and Lamarck to wit, as exponents of 

 the Foraminifera of various earlier Tertiary formations, and by the year 1840, thanks to 

 the labours of d'Orbigny and Ehrenberg, the structure of many rocks of Cretaceous 

 and even of Liassic age had been investigated, and their more or less microzoic character 

 satisfactorily established. 



Somewhat previous to this date, however, that is to say, in the year 1829, Fischer 

 de Waldheim, in his ' Oryctographie du Gouvernernent de Moscou,' 1 in giving an 

 account of the white Carboniferous limestones of Russia, had described the important 

 genus Fusulina. His description and figures are sufficient for purposes of identification ; 

 and, judged with due regard to the state of knowledge at the time, even the structural 

 features of the genus are fairly rendered. Two other minute Carboniferous fossils 

 regarded by Fischer as Foraminifera, and described under the names Spirolinites sulcata 

 and Sp. denticulata, cannot now be identified. The figures do not represent any known 

 type of Rhizopoda, and they have probably been erroneously classed by the author. 



1 For the sake of accuracy, and to avoid needless iteration of details, the titles of all works and papers 

 referred to ars given in full under the head " Bibliography." 



It may here be stated that, for the reasons named in the " Introduction," matters pertaining to the 

 genus Fusulina, when introduced at all, are throughout very cursorily treated. 



