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Updated: May 25, 2025
Thus, for example, the Ammonite, which is not common to older rocks, is represented by no less than seventy-three species; whereas Loxonema, which is only known as common to older rocks, furnishes fifteen Triassic species. Cerithium, so abundant in tertiary strata, and which still lives, is represented by no less than fourteen species.
They overlie the uppermost of an extensive series of Eocene deposits of marine, brackish, and fresh-water formations, which rest on the Chalk and terminate upward in strata corresponding in age to the Paris gypsum, and containing the same extinct genera of quadrupeds, Palaeotherium, Anoplotherium, and others which Cuvier first described. Corbula pisum. Cyrena semistriata. Cerithium elegans.
Thus, there are two species of Cypraea, one of Oliva, two of Mitra, four of the genus Cerithium, six of Fusus, two of Trochus, one of Patella, one of Emarginula, etc.; on the whole, more than thirty univalves, spiral or patelliform. At the same time, some of the accompanying bivalve shells, echinoderms, and zoophytes, are specifically identical with fossils of the true Cretaceous series.
In the clay banks are well-preserved petrifactions, so similar in color, habitat, and aspect to many of those in the German tertiary formations that they might be taken for them. The breccia also is fossil, probably also tertiary; at all events, the identity of the few species which were recognisable in it Cerithium, Pecten, and Venus with living species could not be determined.
In the last-named locality a Cytherea inhabited the mud around their roots. At the Three Islets several new species of Melampus, a Nerita and a Cyrena lived in a like habitat, and at Port Essington Cerithium kieneri, was found in the same situation. The fine Cyrena cyrenoides lives among the roots of mangroves in the Louisiade Archipelago.
Buckland found a large pebble to which five full-grown oysters were affixed, in such a manner as to show that they had commenced their first growth upon it, and remained attached to it through life. Cyrena cuneiformis, Sowerby. Natural size. Syn. Cerithium melanoides, Sowerby.
The prevalence of salt-water remains is most conspicuous in some of the central parts of the formation. Helix labyrinthica, Say. Neritina concava, Sowerby. Lymnea caudata, Edw. Cerithium concavum, Sowerby. Searles Wood in Hordwell Cliff. It is also met with in Headon Hill, in the same beds.
I sent them in search of the shell, and they returned bringing me some living specimens of different shells, chiefly littorina and cerithium. Cerithium palustre. Of the latter the specimens brought to me were dwarfed and solid, exhibiting in this particular the usual peculiarities that distinguish shells inhabiting a rocky locality from their congeners in a sandy bottom.
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