104 CARBONIFEROUS AND PERMIAN FORAMINIFERA. 



impossible to mark off the successive terms of such series by hard lines. The 

 difference in shell-structure between these specimens and the perforate, true NodoisaricR 

 of a neighbouring locality, but of somewhat later geological age, is readily demonstrated 

 by microscopical sections. 



Distribution. Middle Permian Limestone of Tunstall Hill, Durham, rare. Specimens 

 which may be assigned without much hesitation to the same species have been found in 

 the Yoredale Rocks of Wensleydale, and near Skipton, Yorkshire, and somewhat doubtful 

 examples in the Calcaire de Namur of Belgium. 



NODOSINELLA CYLINDRICA, nOV. PI. VII, figS. 4 7. 



Characters. Test cylindrical, nearly straight, sometimes irregular in outline. Seg- 

 ments numerous, cylindrical, but little inflated, usually short. Septation imperfect ; 

 sutures marked externally by slightly depressed lines. Interior of the chambers some- 

 times more or less labyrinthic. Aperture variable, simple or compound. Length 

 -s inch (1-0 mm.). 



A large and somewhat varied series of fossils, agreeing in their irregular, cylindrical 

 contour and their subdivision into numerous short segments, with but little external 

 constriction at the sutures, are included under the name Nodosinetta cylindrica. Many 

 of the specimens are nearly smooth superficially, others quite granular. The smooth 

 varieties are often distinguished with difficulty from fragments of fossils of widely 

 different zoological origin, such as the spines of Echini, or of niolluscan Shells, or even 

 portions of minute Encrinites. Thin microscopical sections often furnish the only means 

 of determining the foraminiferal nature of such organisms. 



The rough varieties, like PI. VII, fig. 7, bear considerable resemblance to some of the 

 recent large deep-sea types of Rhizopoda, especially to Botellina, the difference being 

 chiefly in their comparatively minute size and the consequent finer texture in the 

 labyrinthic lining of the test. 



These slender elongate forms are seldom found quite entire in the Carboniferous 

 beds, and it is necessary to speak with some caution of their minute characters. It is 

 even possible that the group now described may contain representatives of two distinct 

 species. With an insufficient range of specimens it is difficult to apportion a right value 

 to each structural peculiarity, and at present there is not evidence to justify the division 

 of a group which is tolerably uniform in external morphological features. 



Distribution. Hitherto Nodosinella cylindrica has only been recognised in the 

 Carboniferous beds of England and Wales, viz. at Elfhills, and Grassington, in the Upper, 

 and at Bangor, in the Lower division of the Series. 



