Part 2: Researches on the Foraminifera

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                                en lignes longitudinales à l'enroulement spécial"; - whilst
<u>Orbitolites</u> (his definition of which has been already cited, S5)
is placed in the order <u>Cyclostègues</u>.  The separation of the
two genera by so wide an interval, is grounded, therefore,
on the assumption that the type of growth in <u>Orbiculina</u> is
spiral, whilst that of <u>Orbitolites</u> is cyclical.  I have already
shown that this assumption is incorrect as regards <u>Orbito-
lites</u>, <s>its</s> the early plan of whose growth <s>being often</s> is spiral (S54); and I
shall have now to show that it is equally incorrect as regards
<u>Orbiculina</u>, <s>its</s> whose later plan of growth <s>being</s> is typically cyclical.
And often having closely compared these and other types,
we shall be in a position to enquire what value is really
to be attached to such a character as a basis for classification.

83. <u>Organization</u>. - Among the various forms that are
presented by the species before us, it is of course necessary
to select some particular type as that with which others
may be compared; and this I consider to be the form delineated
in Plate I, Fig.7; since by far the larger proportion of the very
numerous specimens I have examined show such a degree
of approximation to it, that their differences may fairly be
set down to the account of <s>age.</s> incomplete development.
The general aspect of a typical <u>Orbiculina</u>, then, differs but
little from that of <u>Orbitolites</u>,  except in the prominence of
its nucleus, and in the peculiar spiral disposition of the
bands by which the surface of the nucleus is marked. The
species never attains, so far as I am aware, the <s>large</s> di-
mentions of <u>Orbitolites</u>, the diameter of the largest recent
disk in my possession (one of Mr Cuming's Philippine spe-
                            
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Manuscript details

Author
William Benjamin Carpenter
Reference
PT/53/8
Series
PT
Date
1856
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Part 2: Researches on the Foraminifera, 1856. From The Royal Society, PT/53/8

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