THE NATIONAL INSTITUTION. 171 



which, for the most part, reliance must be placed on uninformed agents, it will ba 

 absolutely necessary to issue very n»inute instructions, to be observed by tiie col- 

 lector, that they may, with the least expenditure of time, do the best possible with 

 the country they live in. More especially every inducement should be held out to 

 all correspondents to send in wet preparations of the animals which occupy the 

 shells, and dissection of parts, illustrative of their anatomy, preserved in spirits. 



If the National Institution could succeed in establishing branch institutions in 

 the various quarters indicated above, a measure which I would urge upon the early 

 attention of the members, the harvest of species waiting to be gathered in would 

 be accomplished so much the more speedily. 



Respecting the willingness of gentlemen, especially those to whom I have re- 

 ferred, to undertake exchanges, I take this opportunity to bear testimony to the 

 great liberality and promptitude which I have invariably found to actuate natural, 

 ists, though personally strangers to each other. I have attributed these noble 

 qualities as much to the gentle influences exercised by their quiet pursuits, as the 

 wish to extend the humanizing results which always attend the cultivation of 

 science. 



Washington Universitv of Baltimore, Dec. 10, 1841. 



OBSERVATIONS ON A PORTION OF THE ATLANTIC TERTIARY 

 REGION, WITH A DESCRIPTION OF NEW SPECIES OF 

 ORGANIC REMAINS: BY T. A. CONRAD. 



Several circumstances combine to give interest and importance to the tertiary 

 deposits of the Atlantic coast of the Union. These chiefly consist in variations 

 from the usual characteristics of European tertiaries. The first which I shall 

 notice is the remarkable connection of secondary with tertiary, or cretaceous with 

 eocene deposits, by means of the following fossils, which I discovered in a tour in 

 the Southern States in 1832, '33 viz : Nummuliies Mantelli, (nob ;) Gryphcea vomer, 

 (Morton;) Plagiostoma dumosum, (Morton.) The white hmesf one of Alabama, which 

 contains these fossils, is connected with the green-sand formation of IS ew- Jersey, by 

 three species of shells : Ostrea panda, Ostrea cretacea, and Gryphaa vomer, {Ostrea 

 lateralis, Nillson.) The second important disagreement with foreign tertiaries is 

 the absence of any trace of fluviatile remains. The Gnaihodon, a bivalve inhabiting 

 estuaries where the water is scarcely saline, and fresh during the inundations of the 

 rivers, is the only evidence, hitherto obtained, of the occurrence of fresh water 

 streams — a remarkable fact, considering the great extent of land which evidently 

 was present in the tertiary periods. The third peculiarity of the American tertiaries 

 is the abrupt line of demarcation between the fossil groups which they contain ; show- 

 ing no gradual passage or interchange of forms, although the relative levels, above 

 the sea, are of no important variation among the t?iree divisions into which I have 

 grouped the tertiaries, for a convenient but temporary purpose. No one, I pre- 

 sume, would refer this wide difference of zoological character to any relative con- 

 dition of sea or land, caused by earthquakes, or by an elevation of the beds above 

 No. 2 14 



