[71] See my "Thoughts on Animalcules," p. 103.
In the mud of the quicksands on the shore at Brighton, Mr. Reginald Mantell found recent Coscinodisci, &c. associated with fossil polythalamia that had been washed out of the chalk, and precipitated with the frustules of the recent diatomaceæ, into the sediments now in progress.
The prevalence of marine and fresh-water forms in the same deposit is not unusual; and the remarks of Dr. Bailey on this fact are so pertinent, that I insert them, as a salutary caution against hasty generalizations on subjects connected with these investigations. After describing a species of Galionella (G. moniliformis), as an inhabitant only of salt and brackish water, and stating that he had also found it sixty miles up the Hudson River, near West Point, Dr. Bailey observes—"The Fauna and Flora of the Hudson at this place would, if in a fossil state, be rather puzzling to the geologist, on account of the singular mixture of marine and fluviatile species. While Valisneria and Potamogeton (two common fresh-water plants), grow in such vast quantities, in some places, as to prevent the passage of a boat, and the shore is strewn with fluviatile shells (such as Planorbis, Physa, &c.) in a living state, yet the above plants are entangled with Algæ (sea-weeds), and marine parasitic zoophytes; while the rocks below low-water mark are covered with Balani (barnacles) and minute corallines, and the marine Flora is represented by vast quantities of very elegant sea plants."[72]
[72] American Journal of Science, vol. x. p. 41.
I must here close this extended notice of the fossil remains of a class of vegetable organisms, which, though for the most part invisible to the unassisted eye as individual forms, constitute by their inconceivable multitudes an important element in the formation of sedimentary deposits. The fact of their having been formerly treated of as animalcules, and generally regarded as belonging to the animal kingdom, rendered a full consideration of the phenomena necessary, in order to place the subject before the reader in a clear and comprehensive point of view.[73]
[73] As both the recent and fossil frustules of Diatomaceæ are beautiful objects for the microscope and polariscope, they are in much request. Specimens mounted on glass slides may be had of Mr. Topping, and Mr. Poulton. See Appendix.
Confervites.—The cellular aquatic plants named Confervæ are sometimes found in transparent quartz pebbles, and in chalk, appearing as delicate simple or branched filaments, which, by the aid of the microscope, are seen to be articulated. Seven species are described by authors, but the vegetable nature of some of these is doubtful. A beautiful species in Chalk, first noticed by the late Samuel Woodward, Esq. (author of the Geology of Norfolk), is here figured.
