﻿132 CARBONIFEROUS AND PERMIAN FORAMINIFERA. 



Textularia eximia, d'Eichwald. PI. X, figs. 27 — 29. 



Textilaria eximia, d'Eichwald, 1860. Letbsea Rossica, vol. i, p. 355, pi. xxii, figs. 



19, a— d. 



Characters. — Test long, tapering, often curved or irregular in outline ; sub-cylin- 

 drical or only slightly compressed laterally. Segments numerous, six to ten in each 

 series, globose, distinct. Length i ncn mm.). 



In accepting M. d'Eichwald's name as applied to a group of Carboniferous Textularia 

 characterized by their long tapering contour, great thickness in proportion to breadth, 

 and distinct inflated segments, I may have recognised a needless " species," but I can 

 find no earlier description or figures to which this set of forms can be referred with 

 propriety. They belong to the " agglutinans " type, but differ in the shape of the seg- 

 ments and in the tendency to inequilateral growth. Professor Reuss figures a number 

 of somewhat similar varieties from the Cretaceous strata of Bohemia, and of Westphalia, 

 such as Text.fceda from the former, and Text, bolivinoides, T. parallela, T. concinna, T. 

 Partschi, and T. globifera from the latter. These appear to differ from each other chiefly 

 in the amount of lateral compression and in the shape of the terminal chamber, but all 

 of them have the rounded periphery and ventricose segments. 



The mere form of the chambers, and the general aspect of the shell as depending 

 upon it are but slight grounds on which to rest zoological subdivision in so polymor- 

 phic a class of organisms as the Foraminifera, yet most of the so-called " specific " 

 distinctions are dependent on characters of this nature, and when, as in the present 

 case, they indicate a tolerably well-marked group, the expediency of recognising them 

 may be accepted as a matter of convenience without insisting on sharp lines of demar- 

 cation. Without such subdivision the study of the Foraminifera would be impracticable, 

 but it is none the less necessary that the limits of readily ascertained and fairly permanent 

 characters should be observed, otherwise a multiplicity of names, more embarrassing than 

 the inconveniently large groups they were designed to obviate, is the result. 



M. d'Eichwald had but few specimens of fossil microzoa at his command, and his 

 description of Textularia eximia has required some modification to include the finer 

 examples which occur amongst others in our British Carboniferous beds. This appears 

 to be the only variety of the genus which he himself obtained from the Russian lime- 

 stones, though he mentions Text, lunata, Ehrenberg, as a species occurring among sand- 

 grains at Witegra. 



Distribution. — By far the larger number of Carboniferous Textularia have the 



