^! I C R S C P I C A L OBSERVATIONS. 43 



have, therefore, omitted many forms which I could not determine satisfactorily. 

 My guides in studying these bodies, while on the journey, were Ralfs' British 

 Desmidiese, a work whose elaborate descriptions and exquisite figures enable the 

 student to determine the species with perfect certainty; Ktitzing's Diatomaceen 

 Oder Bacillarien, which contains many figures of the Diatomacese, both by 

 Ehrenberg and Kiitzing ; and " Pritchard's History of Infusoria, Recent and 

 Fossil," which contains abridged descriptions and reduced figures, taken trom 

 Ehrenberg's great work, " Die Infusionsthierchen." 



5. The existence of vast quantities of infusorial remains in the earth of the 

 rice fields in the Southern States is, perhaps, connected with their wonderful 

 fertility. The fact that the species found are chiefly marine, and such as now 

 abound in the salt marshes of the coast, indicates the former presence of salt 

 w'ater much farther up the rivers than it now extends. 



6. Although the species found in the rice fields are such as are still living in 

 estuaries or along the coast, those excavated in digging the deep canals of the 

 rice fields, and the ditches of the ibrts near Savannah, must have been deposited 

 many hundreds, if not thousands of years ago, and they are, therefore, fully 

 entitled to the name of fossils, and should, 1 think, be referred to the Post 

 Pleiocene epoch. 



7. The vast salt marsh formations of the coast of South Carolina, Georgia, and 

 Florida abound in silicious Diatomacese, whose shells are daily becoming 

 imbedded in mud ; so that we have here, in the process of formation, deposits 

 similar in character to the infusorial strata of Virginia and Maryland, and quite 

 as extensive, although usually rather more sandy in their character. 



8. It will be seen by table B, that certain species of Diatomacese wiiich occur 

 in the ocean itself, may also live at great distances from the ocean, in estuaries 

 and rivers far above where the surface water is fresh ; yet these same species 

 have never been found in lakes or pools of fresh water, not having a direct com- 

 munication, however remote, with the sea. Among the species of this character 

 are Amphiprora pulchra, B., Amphiprora constricta, Ehr., Amphora libyca, Ehr., 

 Bacillaria paradoxa, Ehr., Ceratoneis closterium, Ehr., Ceratoneis fasciola, 

 Ehr., Coscinodiscus subtilis, Ehr., Cerataulus tui-gidus, Ehr., Navicula elongata, 

 Odontella polymorpha. Kg., and Terpsinoe musica, Ehr. 



9. The beautiful Terpsinoe musica, Ehr., is an interesting addition to our 

 native species of Diatomacese. It was first received by Ehrenberg from Mexico, 

 and he has recently proved its existence in the rivers of Texas, (see Monats- 

 bericht der Preuss. Akad. zu Berlin, Feb., 1849, p. 88 ;) but it was not known to 

 exist in the older States until, by the observations recorded in this memoir, I 

 determined its existence in all our Southern rivers. I have also specimens of it 

 from Jamaica, West Indies, and portions of a closely allied, if not identical form, 

 from Mindanao, in the Phillipiiie Islands. 



