﻿VALVULINA. 



85 



Distribution. — Of all the smaller Carboniferous Foraminifera Valvulina palceotrochis 

 is perhaps the commonest and most generally diffused — the only columns in the 

 Carboniferous portion of the General Summary of distribution in which its presence is 

 not indicated are those (but two in number) in which the quantity of material available for 

 examination has been very limited. The species has not hitherto been found in beds of 

 Permian or later age. 



Valvulina pal^otrochus, var. compressa, Brady. PI. IV, figs. 5, a, b. 



Valvulina pal^otrochtjs, var. compressa, Brady, 1873. Mem. Geol. Survey Scot- 

 land; Expl. Sheet 23, pp. 61, 95, &c. 



In a few localities there occur, associated with the typical Valvulina palaotrochus, 

 specimens presenting the same general characters, but having an elongated oval, instead 

 of a circular, transverse section ; in other words, having the form of a cone which might 

 have been altered in shape by lateral compression. Such specimens are slightly smaller 

 than those of the type ; they are uneven, and one-sided at the base, more deeply 

 excavated on the inferior surface at the umbilicus, and the sutural depressions marking 

 the septa are somewhat stronger. There is no satisfactory evidence either in the external 

 appearance or in the transverse section that the oval contour is really the effect of 

 pressure. I have elsewhere 1 noted that, where change of shape in organisms of this sort 

 has been produced by crushing, there is little difficulty in tracing the fact in the fracture 

 or interruption of the spiral band at the ends of the longer diameter of the transverse 

 section. In some habitats, where the circular, typical form is abundant, the oval 

 variety is conspicuously absent, whilst in one or two localities they occur in almost 

 equal proportions. There is no need to attribute more than subvarietal importance to 

 these minor characters, but it may be well, till we know something more about 

 them, to distinguish the compressed forms by a trivial name subordinate to V. 

 palcsotrockus. 



Distribution. — Found in a limited number of localities, in the higher and lower 

 division of the Carboniferous Limestone in England, and in the Upper and Lower 

 Carboniferous Limestone Groups of Scotland ; not recorded elsewhere. 



1 « Phil. Trans.,' 1869, p. 754, pi. lxxx, fig. 2. (In Lo/tusia.) 



