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Akad. zu Berlin" April 1845: POLYGASTRICA. Fragilaria rhabdosoma. Gallionella distans. Pinnularia? PHYTOLITHARIA. Lithodontium Bursa. Lithodontium furcatum. Lithostylidium exesum. Lithostylidium rude. Lithostylidium Serra.
This substance, when dry, is tolerably compact, and of little specific gravity: Professor Ehrenberg has examined it: he states "Konig Akad. der Wissen" Berlin February 1845, that it is composed of infusoria, including fourteen polygastrica and four phytolitharia.
In some of the red mud scraped from a tooth of one of the Mastodons at Gorodona, Professor Ehrenberg finds seven Polygastrica and thirteen Phytolitharia, all of them, I believe, with two exceptions, already known species. Akad. zu Berlin" April 1845. The list consists of: POLYGASTRICA. Campylodiscus clypeus. Coscinodiscus subtilis. Coscinodiscus al. sp. Eunotia. Gallionella granulata.
PHYTOLITHARIA. Lithasteriscus tuberculatus. Lithostylidium Clepsammidium. Lithostylidium quadratum. Lithostylidium rude. Lithostylidium unidentatum. Only one of these eight microscopical bodies is common to the nine from Monte Hermoso: but five of them are in common with those from the Pampean mud on the banks of the Parana.
The bottom of the sea, I may remark, to a distance of several miles from the shore, and to a depth of between sixty and one hundred feet, was found by the anchors to be composed of tosca-rock and reddish Pampean mud. Professor Ehrenberg has examined for me specimens of the two lower beds, and finds in them three Polygastrica and six Phytolitharia.
Phytolitharia were numerous, as also 'neatly-lobed vegetable scales; which, as Ehrenberg observes, is sufficient to disprove the assertion, that the substance is formed in the atmosphere itself, and is not of European origin.
Professor Ehrenberg has examined for me specimens of the finer matter from in contact with these mammiferous remains: he finds in them two Polygastrica, decidedly marine forms; and six Phytolitharia, of which one is probably marine, and the others either of fresh-water or terrestrial origin. The list consists of: POLYGASTRICA. Gallionella sulcata. Stauroptera aspera? fragm.
In the dust collected from these various falls, there have been found altogether nineteen species of infusoria; of which eight were polythalamia, seven polygastrica, and two phytolitharia, these chiefly constituting the flint-earth portion of the dust.
Of the thirteen Phytolitharia, nine are met with in the two deposits in Bahia Blanca, where there is evidence from two other species of Polygastrica that the beds were accumulated in brackish water. The traces of coral, sponges, and Polythalamia, found by Dr.
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