NUMMULITES. 345 
in many of the early works on petrifactions. They occur 
in immense quantities in certain rocks, and are of all sizes, 
from a mere point, to disks an inch and a half in diameter ; 
thus exceeding in magnitude all other animals of this class. 
Perfect specimens appear as a calcareous solid circular 
body, of a lenticular shape ; smooth, and slightly convex on 
both sides, and without any visible structure. On splitting 
4 fossil transversely, or rubbing down one of the convex 
; planes, a series of minute cells, arranged in a discoidal spire, 
is brought to view, as shown in Lign. 110, fig. 1. But this 
: description gives a very inadequate idea of the complicated 
and exquisite structure of the original, which has been 
eceebly worked out by Dr. Carpenter. This eminent 
physiologist has shown that each chamber was occupied by 
° living segment, connected with other segments by one or 
more tubular prolongations, which absorbed nutrition from 
without, by means of filamentous pseudopodia, that projected 
ae a system of passages leading from the medial plane 
to the external surface.* A figure of the supposed form of 
= living Nummulina is given in Pict. Atlas, p. 187. 
_ The specimens figured in Zign. 110 are from the lime- 
stone that forms the foundation rock of the Great Pyramid 
¥ Egypt, and of which that structure is in great part com- 
i posed. Strabo alludes to the Nummulites of the Pyramids, 
“as lentils which had been scattered about by the artificers 
“employed on those stupendous monuments, and* become 
‘Stone.t Silicifiedsmasses of Nummulites are occasionally 
* Geol. Journal, vol, vi. p. 21. See also a paper by Prof. William- 
son, “On the minute Structure of the Calcareous Shells of some 
‘recent species of Foraminifera.” Trans. Microscop. Soc. vol. iii. 
?p. 105. 
_ ¢ An interesting fact was communicated to me by a friend who 
lately descended the Nile; the Nummulitic limestone rocks are in 
some parts of the course of the river washed into the stream, and 
“becoming disintegrated, the Nummulites are set free, and re-deposited 
in the recent mud of the Nile. 
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ee 
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