REPOET ON THE FORAMINIEERA. 
287 
make it brittle. In certain genera of the Lituolesle the visible test or skeleton is supple- 
mented and strengthened by the extension of the walls into the interior, in the form of 
irregular ramifying secondary septa, constructed like the remainder of the test of cemented 
sand-grains. This subdivision of the chamber-cavities is characteristic of the genera 
Lituolci, Hajplostiche, and Bdelloidina. 
Amongst the Trochammentdee a very different rule prevails. The typical test is 
composed of exceedingly fine sand with an excess of cement ; and the walls are thin, well 
finished, and smooth externally. Sometimes amongst the larger species a few projecting 
sponge-spicules mar the otherwise even surface, but more commonly the test is perfectly 
smooth and glossy, and, unlike that of the Lituoline forms, might be spoken of with pro- 
priety as a “ shell.” The most important divergence from the typical structure occurs in the 
case of certain Trochammincs which inhabit brackish water. In estuarine pools, and other 
localities where the proportion of saline constituents in the water is less than in the open 
sea, the tests of the Trochammince become less calcareous, and this diminution may 
continue until the investment is little more than a chitinous envelope, so thin and flexible 
that it collapses on being taken out of fluid and allowed to dry. 
Of the structure of the Endothyresee it is necessary to speak with considerable 
caution, inasmuch as the Sub-family contains none but fossil species, and they are for the 
most part only found in the older calcareous rocks. So far as can be made out, the test, 
though more or less distinctly arenaceous, contains a much larger proportion of calcareous 
cement than is noticed in either of the Sub-families previously described ; and a certain 
limited number of species appear to have perforated walls. The shell is generally thin, 
but in rare instances the inner surface is more or less cancellated. 
In the Sub-family Loftusiisle the test is characterised by its great thickness and its 
cancellated structure. Of the three genera which it includes, two are known only by 
fossil specimens, and so far as they are concerned the chemical composition of the living 
tests cannot be stated with certainty ; the third, Cyclammina, is constructed of fine 
siliceous sand, cemented by means of a compound containing a large proportion of peroxide 
of iron. But the conspicuous feature of the entire Sub-family is not so much the chemical 
nature of the investment as its structural peculiarity, in that it exemplifies the fullest 
development of what is known as the labyrinthic or cancellated variety of shell-structure . 1 
1 I am well aware, of course, that the Rhizopodal nature of Parkeria and even of Loftusia has been called in question ; 
hut have seen no evidence which, so far as I can judge, contravenes in any way the general accuracy of the observa- 
tions and conclusions set forth in the original description of these genera. With regard to Loftusia, the minute 
structure is that of Cyclammina, the contour that of Alveolina, and I am persuaded that but for its comparatively large 
size, its foraminiferal character would never have been demurred to. Prof. P. Martin Duncan’s researches on the 
Syri/ngosphceridoe, a group of fossils closely allied to Parkeria, tend to confirm the views originally expressed as to its 
zoological position, and the occurrence of a porcellanous isomorph, in Keramospluera, has an interesting hearing in the 
same direction. Finally, since the present sheets have been in the hands of the printer, the discovery in the living 
condition of Syringammina, a well-characterised Rhizopod, with arenaceous test similar in form and dimensions to 
Parkeria, and exhibiting structural features in many ways analogous, helps to remove any lingering doubt on the subject. 
