Carhoniferous Foraminifera. By Bev. W. Howchm. 537 



six chambers, foiir ef wliich are commonly visible externally ; chambers 

 globose, increasing rapidly in size, the final segment very large, 

 slightly overlapping and generally equal in size to the rest of the 

 shell, giving a ventricose appearance to the oral extremity. Septal 

 divisions often confused and labyrinthic. External surface rough. 

 Aperture compound or cribriform, very distinct, and situated on the 

 convex surface of final segment. Diameter of globose example 

 1/50 in. ; subcylindrical, 1/30 in., long diameter. 



This form is easily distinguished from Lituola Bennieana, Br. by 

 its much smaller size, more rounded form, the fewness of its chambers, 

 their greater inflation, and the position of its compound aperture. 

 The aperture, which generally is very clearly visible, occurs, not on 

 an incurved septal face, but on the convex part of the final segment, 

 suggestive of a rectilinear growth. Fig. 5, whilst a fairly typical 

 example in other respects, exhibits this feature in a less degree than 

 the average number of specimens. The tendency to variation in this 

 species is in the direction of a partial uncoiling of the spke, and some 

 individuals even exhibit intermediate gradations with the crozier- 

 shaped members of the genus. A comparison of the transparent 

 vertical section given of L. Bennieana, Plate VIII. fig. 7, with a 

 similar section given of the present species, Plate VIII. fig. 6, will 

 give a fair idea of the distinctive features of their internal structure. 

 The only form with which L. rotundata is likely to be confounded in 

 the Carboniferous shales, is Valvulina hulloides, Br. I have not had 

 the good fortune to obtain this latter form from the district concerned 

 in the present investigations ; but, judging from Mr. Brady's excellent 

 drawings, the concave surface of the oral extremity of Valvulina 

 hulloides, as well as the very distinctive apertures, in each case, would 

 be easy guides to their identification. 



Bistrihution. — It is not a very frequent form. It is rare in the 

 Great Limestone of Curry Hill, Allendale; moderately common in 

 the " D " Limestone of the Tipalt, and was recognized in transparent 

 sections of the "K" Limestone, Cowburn. 



Lituola Bennieana, Brady. Plate YIII. fig. 7. 



In the schemes of classification where the perforate or imperforate 

 character of the test was made a ground of primary division among 

 the Foraminifera, the genus Lituola was placed among the " Imper- 

 forata." Mr. Brady's reasons for rejecting this principle of classi- 

 fication receive from time to time additional justification. The 

 artificial nature of this method of division has received conspicuous 

 illustration in that, whilst the LituoHdse are normally imperforate, 

 the large Carboniferous species, L. Bennieana, is frequently coarsely 

 perforate. This has been demonstrated by several sections made 

 both in horizontal and vertical directions, in which the perforate 

 character of the test is equally manifest. Plate YIII. fig. 7 

 is one such section, taken vertically, which also shows, in this 

 individual, an aperture at the inner margin of the terminal segment. 



