338 
REVIEWS. 
Genus 1. Ampliistegina. 
,, 2. Operculina 
„ 3. INTummulina. 
„ 4. Polystomella. 
Nonionina. 
Genus 5, Heterostegina 
,, 6. Cycloclypeus. 
„ 7. Orbitoides. 
,, 8. Eusulina. 
It will be seen that this classification is distinguished at once by 
positive and negative characters. Eirst, as to the former, Dr. 
Carpenter’s two primary divisions rest upon an appreciation of 
almost the only possible difference in ‘ plan of structure,’ which in 
animals so simply organised as the Eoraminifera could be expected 
to occur- This, in its turn, involves a corresponding difference as 
to the relation subsisting between the soft animal body and the 
medium wherein it lives. The relation of the shell itself to the sar- 
code substance, and of its several chambers to one another, among the 
polythalamous forms, are, by the same comprehensive distinction, 
also reorganized. The families of the higher sub-order, Perforata , 
are differentiated from one another by minor modifications of those 
very characters on which the sub-order itself has been esta¬ 
blished, while in the Imperforata the texture of the shell, whether 
membranous, calcareous, or arenaceous has been taken into account. 
Many will doubtless regard Dr. Carpenter’s genera as too con¬ 
densed, and find fault with his opinion of the wmrthlessness of 
specific distinctions within the Eoraminiferous group. Let such 
persons, however, proceed to study these animals for themselves and, 
sooner or later, they will not fail to become convinced that “ sharply - 
defined divisions —whether between species, genera, families, or 
orders— do not exist among Foraminiferal Who can absolutely 
distinguish between Orbiculina and Alveolina , widely dissimilar as 
are these genera in their extreme forms from one another ? The 
two great families Globigerida and Nummulinida have their charac¬ 
ters united in such genera as Ampliistegina and Rotalia. Even 
the sub-orders Perforata and Imperforata are brought together by 
Yalvulina , a genus which may well be considered as occupying an 
intermediate position “ since, although its shell is constantly arena¬ 
ceous, and is (for the most part) practically imperforate, yet it is 
formed on the basis of a perforated vitreous lamina.” 
Among the negative characteristics in Dr. Carpenter’s arrange¬ 
ment, the small value therein attached to direction of growth and the 
distinction between monothalamous and polythalamous shells , should 
most prominently be mentioned. Let it be remembered that two 
Eoraminifera, having the same direction of growth, and consequently 
the same extreme form, may differ in almost every other respect. 
It is by no means rare for shells to change their direction of growth 
as they become older, and we have already hinted that even 
different parts of the same specimen may appear to point to two dis¬ 
similar modes of increase. Among the higher Eoraminifera, the 
direction of growth varies with some approach to regularity, and, 
