﻿140 CARBONIFEROUS AND PERMTAN FORAMINIFERA 



General Characters. — Test free, spiral, typically bi-convex and trochoid, but varying 

 from this to depressed, complanate, or even vermieulate ; composed of few convolutions, 

 all of which are visible on the superior lateral surface ; the inferior surface nearly or 

 entirely occupied by the last convolution. Segments less numerous than in the other 

 Rotalina, varying from 7 to 26 in number. Shell very finely porous and almost 

 destitute of canal-system ; sutures often limbate, sometimes granulate ; the limbation 

 of the sutures frequently accompanied by further exogenous deposit in the form of a star 

 radiating from the umbilicus. Margin angular or subcarinate. Aperture large, variable, 

 often arcuate and notched, situate on the outer edge of the inferior surface of the 

 terminal segment near the umbilicus. 



Only a few small obscure specimens referrible to the genus Pulvinulina have been 

 found in Carboniferous deposits. These are described under the name Pulvinulina 

 Broeckiana. The genus has been long known to exist as far back as the Trias, and from 

 that period through succeeding geological eras it is represented by a gradually increasing 

 number of species. The type still furnishes some of our most common deep-sea 

 Rhizopoda. 



Pulvinulina Broeckiana, nov. PI. VI, fig. 12. 



Characters. — Test orbicular, depressed ; superior side only slightly convex ; inferior 

 more strongly so; margin carinate. Spire composed of about three convolutions. 

 Upper surface smooth, sutures marked only by broad dark lines of clear shell-substance ; 

 inferior surface more or less granular or tuberculate, sutures marked by slight depres- 

 sions. Diameter ^ inch (0'65 mm.). 



In many particulars this form, with which I have had the pleasure of associating the 

 name of my friend M. Ernest Vanden Broeck, of Brussels, to whose kindness I owe, 

 directly or indirectly, all the Belgian Carboniferous material I have had the opportunity 

 of examining, closely approaches the characters of Pulvinulina elegans, d'Orbigny ; a fact 

 the more interesting because that species and the allied P. cassiana (Giimbel) are 

 amongst the oldest of the true Rotalina, which have hitherto been satisfactorily identified. 

 Messrs. Parker and Jones found minute specimens of the former in abundance in the 

 alabaster pits of Chellaston, Derbyshire, in a marl probably of later Triassic age ; l whilst 

 Dr. Giimbel records the latter from the Trias of the Alps. The Carboniferous form is 

 much less convex on its superior surface than P. elegans, and does not possess the 

 characteristic limbation of the sutures ; the tuberculate condition of its inferior surface is 



1 ' Quart. Journ. Geol. Soc.,' I860, vol. xvi, p. 455, pi. xx, fig. 46, under the name Rotalia elegans. 



