744 
DE. W. B. CAEPENTEE AND ME. H. B. BEADY ON 
ances presented by the actual specimens. The process of infiltration, which has in 
every instance extended to every part of the organism, has obscured its most important 
peculiarities. Fortunately in the discovery of ParJceria , and in the results of Dr. Carpen- 
ter’ s researches on this new and most interesting type of Foraminifera, we find a clue to 
the reading of several portions that would otherwise have remained unintelligible. Many 
of the specimens of Parkeria are completely infiltrated with a sub crystalline mineral, 
very similar in physical characters to that occurring in the chambers of Loftusia. But 
there are others, which, either from the nature of the matrix, or from the compact 
texture of the peripheral layer of the test, contain no such deposit ; but remain, as nearly 
as can be judged, in the state of a dead and empty recent shell. In addition to these, 
a few examples of Parkeria have been met with partially infiltrated ; only their exterior 
layers having been consolidated by mineral deposit. Each of these three sets of speci- 
mens has added its quota to the facts upon which the elucidation of a somewhat com- 
plex organization depends ; and each has a distinct value in the study of Loftusia. By 
comparing the appearance of corresponding portions of the infiltrated and uninfiltrated 
test in Parkeria , reliable data are obtained from which to estimate the condition of 
Loftusia prior to the filling up of its cavities with inorganic matter. Constant compa- 
rison with the less altered type has been found needful, in order to demonstrate the 
organization of the more obscure form ; and for the opportunity of pursuing the subject 
in this way I am indebted to the kindness of Dr. Carpenter. 
32. The texture of the 4 test’ has been stated to be Arenaceous, that is, built up of sand- 
grains held together by a structureless calcareous cement. It is only necessary to refer 
to it in this place, in so far as it affects the relation of the walls to the sarcode-cavities. 
The granules vary considerably in size, but are comparatively much larger than those 
from which the investment of Parkeria is formed; hence in the transparent sections of 
Loftusia the texture does not appear so homogeneous, nor is the outline of the laby- 
rinthic ingrowths so well defined ; indeed it is obvious that in the recent condition the 
interior surfaces could not have had the same smooth finish that is to be observed in the 
open portions (‘ interspaces ’) of Parkeria. 
33. After careful examination of a large number of sections of Loftusia , made on the 
median line in both a transverse and a longitudinal direction, I find no indication of the 
existence of a central cavity, or anything resembling the large primordial chamber which 
is so usual a character amongst the Foraminifera. The tendency to fill up the interior 
of the chambers with shelly ingrowths, which leads to some of the most striking pecu- 
liarities of its organization, is manifest from the very earliest period of life. We have 
no very young specimens from which to study the condition of the test before it assumes 
the form and habit of maturity, except such rare instances as may be found in micro- 
scopical sections of the limestone matrix, and these are far from satisfactory. One 
section of the rock, figured at Plate LXXVIII. fig. 5, shows, however, amongst other 
minute fossils, the transverse section of what I have little doubt is a very young Loftusia(a). 
The whole is about in. in diameter, and shows the space enclosed by the first turn 
of the spiral lamina, and about half the circuit of the layer immediately surrounding it. 
