Part 2: Researches on the Foraminifera

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                                specimens of the same type; for in them we find the superfi-
cial cells differentiated from the intermediate layers (Fig. 21, <u>a</u>) precisely
as in <u>Orbitolites</u>.<sup>X</sup>  Looking to the far larger dimensions which
these fossils present (S83) as compared with the existing spe-
cimens of <u>Orbiculina</u>, <s>and to the fact that they are</s> I am dis-
posed to believe that this <s>genus</s> type attained its highest develop-
ment <s>at the</s> in a period long since passed; and that we
now have, so to speak, only the degenerate descendants of <s>the</s>
an ancestry of higher rank; whilst in the case of <u>Orbitolites</u>, I am
<s>disposed</s> inclined to think that the type is most fully evolved at the
present time.

91. <u>General Conclusion</u> - From the foregoing details it is obvious that the
relationship between <u>Orbitolites</u> and <u>Orbiculina</u> is ex-
tremely close; the only essential point of difference between
them being that which is furnished by the structure of the
nucleus. Whether <u>or not</u> they ought to rank as types of <u>distinct
genera</u>, or whether they ought (as Prof. Williamson main
tains) to rank as  <u>cognate species</u> of the same genus, is a point
as to which it is impossible to arrive at a satisfactory con-
clusion, until the characters which should serve for the dis-
tinction of genera and species in this class shall have been
<s><u>rightly</u></s> determined on a physiological basis. This much I
think myself entitled to assert with confidence, - that even
if they are regarded as distinct genera, they must be
- - - - - - - -
X Although Mr Carter has described this fossil as a species
of <u>Orbitolites</u>, yet it is really an <u>Orbiculina</u>, as is shown by the
spiral conformation of its central portion (Fig.25), and by the in-
vestment afforded by each turn of the spire to its predeces-
sor, as shown in Fig.24<u>a</U>.


                            
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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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