Part 2: Researches on the Foraminifera

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                                90. Again, by examination of the natural margins
of <u>Orbiculina</u> (Figs. 13, 24, 26), and by a comparison of these with
vertical sections (Figs. 22, 23), it becomes evident that the same
variety exists as in <u>Orbitolites</u> in regard to the increase of the
disc in thickness by the vertical elongation of the segments
of sarcode. For <s>in</s> some specimens are altogether conforma
ble to the 'simple type' of <u>Orbitolites</u>, in having but a single
floor of chambers (so to speak), with a singe row of margi-
nal pores; <s>and</s> whilst others correspond with the complex type of
<u>Orbitolites</u>, in having many such floors, with numerous
rows of marginal pores. In the former, the segments of sarcode
<s>would resemb</s> with their singular annular <s>canal</s> stolon, would re-
semble bead strung at short distances on a cord. In the
latter the segments would be columnar, with constrictions
at intervals, and would communicate with each other by
two or more annular stolons. - It is true that we seldom
find any such complete differentiation of the superficial cells, as
the fully-developed type of Orbitolites presents; but when we have
seen that such differentiation is by no means a constant
character in that genus (S50); and the structure of the most
developed specimens I have examined among the recent
<u>Orbiculina</u> closely corresponds in this respect with that
of the fossil Orbitolites of the Paris basin, as will be seen
on comparing the left-hand portion of Fig.22 with Plate VI,
Fig.11 of my former Memoir.  But it is not a little remarkable,
that while the fossil <u>Orbitolites</u> of the Paris tertiaries <s>should</s>
are <u>less</u> developed in this respect that their existing repre-
sentatives in the South Seas, the fossil <u>Orbiculina</u> of the
Malaban tertiaries should be <u>more</u> developed than existing
                            
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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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