558 
DR. carpenter’s RESEARCHES ON THE FORAMINIFERA. 
102. The shelly plates which hound the chambered plane above and below, are 
formed of a succession of superimposed lamellae (Plate XXXI. fig-. 10). These lamellae, 
which are of tolerably uniform thickness, are most numerous in the older or more cen- 
tral portions of the disk, and diminish in number towards the marginal or last-formed 
])ortions ; so that it seems pretty certain that new lamellae must be added from time 
to time, as the disk is augmented by the formation of new annuli. I have often met 
with appearances, which might seem to indicate that the formation of a new lamella 
over the entire surface of the disk, and the addition of a new annulus at its margin, 
were parts of one and the same act of growth, the new lamella being continued into 
the annular septum; but if this were constantly the case, the number of lamellae 
which form the ceiling or floor of any chamber, would always correspond with the 
number of annuli external to it, which I do not find to hold-good. 
103. Each of these lamellae is perforated by an assemblage of parallel tubull very 
closely set-together, which pass from its inner towards its outer surface (Plate XXXI. 
figs. 9, 10); and there is such a continuity between the tubuli of successive lamellae, 
that a communication is thus established between the cavity of the thickest-walled 
chamber, and the external surface of the disk. These tubuli, how’ever, are very mi- 
nute, tlieir diameter being not above inch. They are wanting in cer- 
tain parts of the shell, whicli then presents a transparence that contrasts strikingly 
w^ith the semi-opacity produced by the tubular perforations. By the comparison of 
vertical with horizontal sections taken in different planes, it appears that these trans- 
])arent portions of the shell have a conical form, the base of each being on the sur- 
face of tlie shell, and its apex pointing to one of the angles at the outer margin of a 
chamber (Plate XXX. fig. 4, cc, c?c?). Their gradual widening towards the surface 
causes the diameter of their bases to increase w^ith every addition to the thickness of 
the shell ; and thus it is on the older portion of the shell, and especially on its cen- 
tral protuberance, that they become most conspicuous as lounded ‘ punctations ’ 
(§96). In horizontal sections of the superficial lamellae, they form a large proportion 
of the area (Plate XXXI. fig. G) ; whilst in similar sections near the chambered plane 
(fig. 9), they become blended with angular projections of the annular partitions, that 
fill-uj) the spaces left between tbe proper walls of the chambers by the rounding-off 
of their angles. 
104. The lamellated structure is seen in these conical pillars (Plate XXXI. fig. 
10, Z/), the lamellae being continuous with those of the tubular part of the shell; so 
that at each increase in thickness, a tubular and a non-tubular portion must be super- 
imposed upon the corresponding parts of the preceding lamella. Both in the tubular 
structure of the shell, and in the j)resence of these non-tubular columns, there is an 
exact conformity to the structure N'ummidite and its congeners*. 
* I avail myself of this opportunity of correcting a mistake into which I fell in my original description 
of the structure of Nummulite (Quart. Journ. of Geol. Soc., 1850, p. 26), in regarding the non-tubular 
columns of the shell as having been passages which had become filled-up by the infiltration of carbonate of lime 
