﻿AMPHISTEGINA —NUMMULINA. 



147 



diameter of ^ of an inch (0*8 mm.) ; so that in the absence of prominent structural 

 peculiarities, its diminutive size may be taken as a basis for its specific name. 



The almost identical dimensions of the specimens of the allied types Nummulina and 

 Archcediscus would make it appear that relatively small size is the normal character of 

 the Carboniferous representatives of all three genera. 



Distribution. — Only found hitherto in the " Foraminifera Bed " of the Upper 

 Mountain Limestone, Leigh Woods, Bristol. 



Genus. — Nummulina, d' Orbigny. 



Nummulina, d'Orbigny, Ilichelotti, Bronn, Galeotti, Buvignier, Carpenter, Williamson, 



Bornemann, Parker and Jones, Seguenza, Gilmbel, Brady, fyc. 

 Nautilus, Ammonites, Helicites, Camerina, Discolithes, Phacites, Nummulites, 



Lenticulites, Rotalites, Lycophris, Nummularia, Egeon, Assilina, auctorum. 



General Characters. — Shell free, spiral, equilateral or sub-equilateral, regular, 

 rounded : typically, discoidal, lenticular. Convolutions embracing, the last enclosing 

 those preceding it. Segments numerous, V-shaped, the later ones, in mature shells, 

 gradually contracted at the peripheral margin so that the ultimate convolution loses 

 itself in the penultimate. Aperture single, simple, close to the periphery of the preceding 

 convolution. 



Any general history of the genus Nummulina would be misplaced in a paper 

 relating primarily to fossils of the Carboniferous period; nor is there the necessity 

 to enter at length upon a subject which has already been exhaustively treated in many of 

 its aspects in the well-known works of Joly and Leymerie, d'Archiac and Haime, 

 Williamson, Carpenter, Carter, Rupert Jones and Parker, and others. Anything that 

 could be said within the space that could properly be devoted to it here would be but 

 an imperfect abstract of the writings of such authors. At the same time the occurrence 

 in Palaeozoic beds of undoubted examples of a type of animal life for long regarded as 

 peculiar to the Tertiary epoch can scarcely be introduced without some notice of other 

 recorded Prsetertiary Nummulites, even though it be, in part at least, a repetition of what 

 has already appeared. 



In 1849 Rouillier and Vosinsky 1 described under the name Nummulina antiquior an 

 unsymmetrical Poraminifer from the white Carboniferous limestone of the neighbourhood 

 of Moscow. In 1861 d'Eichwald, 2 supplied with specimens, as I understand, by these 



1 'Bulletin Soc. Imp. des Naturalistes de Moscou, vol. xxii, p. 337, tab. K, figs. 66 — 84. 



2 'Lethsea Rossica,' vol. i, p. 352, pi. xxii, fig. 16. 



