In one specimen, (figured in _Philos. Trans._ 1846, pl. xxi. _fig._ 10,) the membrane of the largest sacs is much corrugated, and disposed in numerous duplications, probably owing to the empty state of these segments, when immersed in the chalk; but the discoidal contour of the original is well preserved. This fossil so closely resembles the decalcified body of a recent Rotalia or Rosalina, that an eminent observer who saw it under the microscope at the meeting of the Royal Society, without knowing its history, concluded it to be the body of a recent animal. This extraordinary preservation of the soft delicate tissues of an animal of the cretaceous seas, invisible to the unassisted eye, through the incalculable ages that must have elapsed since the deposition of the chalk in which it was enshrined, is a fact as remarkable as the occurrence of the carcass of the Lena Mammoth, in the frozen soil of Siberia. [Sidenote: FORAMINIFERA IN CHALK AND FLINT.] [Illustration: Lign. 119. Remains of Foraminifera; in Chalk and Flint. (_Viewed by transmitted light; highly magnified._) Fig. 1.--Shell of a Rosalina, filled with mineral matter; in flint. 2.--Soft parts of a Textularia; in flint. 3.--Cells of Textularia elongata; filled with mineral matter; the shell not visible; in flint. 4.--The soft body of a Rotalia, deprived of its shell, and partially uncoiled; obtained from Chalk, × 450 _diameters_. ] The soft parts of other foraminifera have been discovered in a similar state of preservation. A fine example of the body of a Textularia, in flint, is figured, _Lign. 119, fig. 2_. The form and disposition of the segments in _Textularia elongata_, is shown in _Lign. 119, fig. 3_. These cells are filled with inorganic matter. The shell of a Rosalina filled with an opaque mineral substance, forming casts of the cells, is represented in _Lign. 119, fig. 1_. The preservation of the soft parts of foraminifera and of mollusks, in a fossil state, is a phenomenon of frequent occurrence, and no longer questioned by geologists, notwithstanding the scepticism with which my first announcement of the fact was received. Dr. Bailey, of West Point Military Academy, soon after the publication of my first paper, sent me specimens from the marls of New Jersey.