194 Brady— On Involutina Liassica. 
a condition suitable for study. Again, in certain shales which 
abound in Warwickshire, these little fossils are so loosely im- 
pacted that they can be easily picked out; and the largest 
specimens I have seen were collected in this way near Rugby 
by the Rev. Fred. Smithe, F.G.S., of Noake Court. 
The structure of the organism and its relationships are most 
easily recognized in the middle-sized and smaller specimens washed 
out of clays. It consists essentially of a tube, somewhat increasing 
in diameter, coiled upon itself in a horizontal plane,—or perhaps, 
more correctly speaking, of a tube, with a portion of its periphery 
cut out, coiled upon itself, as it is only a tent-like covering for the 
sarcode, increasing in length with the growth of the animal. The 
shell-wall is not double between the successive coils of the spire, as 
is the case in the true Rotaline. Much exogenous deposit of shell- 
substance takes place upon the dise thus formed, sometimes covering 
the entire surface, but more usually leaving the outermost circle of 
the tube bare. This thickening does not occur with evenness or 
regularity; but, in addition to its general tendency towards the centre 
of the disc (which gives the bi-convex contour), it takes the form 
of irregular tubercles, which sometimes almost cover the sides. 
The peculiar structure of the shell-walls may be seen in the outer- 
most whorl of the spire, or in any portions which remain free from 
external deposit. Microscopical examination shows that it is not 
homogenous in texture, but composed of arenaceous grains embedded 
in the calcareous shell-substance, indicating, together with certain 
other characters shortly to be mentioned, a much lower organization 
than that possessed by the Nummulitic group. 
The open end of the tube seems to act as the general aperture ; 
but if a horizontal section be made, by grinding away a portion of 
the two sides of a specimen, we have distinct traces of pseudopodial 
perforations on the inner surface of the walls, though these are con- 
cealed externally by sandy particles, more or less incorporated in the 
shell-substance (see Pl. IX. fig. 6). A glance at the same section 
also shows the very partial and irregular development of the septa; 
indeed many specimens appear to be almost devoid of any division 
into chambers. Some horizontal sections seem to indicate that the 
septa, or imperfect partitions, are not formed on the same plan that 
prevails in the higher forms of Foraminifera, but that they are 
essentially plaits or infoldings of the outer shell; and their irregu- 
larity in number, extent of development, and position, are dependent 
on their peculiar mode of growth. The accompanying wood-cuts 
explain more fully what is meant. Fig. 1 is a diagrammatic repre- 
sentation of one of the sections alluded to; and fig. 2 is a more highly 
magnified diagram of a portion of the shell-wall, showing the mode 
in which the infolding occurs, forming the septa. 
The transverse section (Pl. IX. fig. 5) gives evidence only of the 
course taken by a simple tube, rounded or more or less semicircular 
in section, as it forms the central disc of the shell, the remainder 
being, at any rate in the Fretherne specimens, occupied by irregularly 
