LIST OF DIATOMACEiE FROM A DEEP-SEA DREDGING IN THE 

 ATLANTIC OCEAN OFF DELAWARE BAY BY THE U. S. FISH 

 COMMISSION STEAMER ALBATROSS. 



BY 



Albert Mann. 



In presenting this list of sj)ecies of the Diatomacenp, accompanied 

 with mounted specimens, which I have discovered in the first of the 

 deep-sea Atlantic dredgings submitted to me for examination, I wish 

 to oflFer some general results of the investigation. 



This dredging was taken by the United States steamer Albatross at 

 Station No. 2721, being in latitude 38° 56' 00" N. and longitude 72© 11' 

 30" W., and in 813 fathoms of water. The species found (numbering 

 145, and with varieties 150) comprise not only marine forms, but a large 

 number that are known to be fresh-water, and some found hitherto 

 only in a fossil state. 



Before treating the material with acids I carefully examined it as it 

 was sent to me, i>reserved in alcohol, and discovered that none of the 

 frustules contain a particle of endochrome or organic inatter. This, 

 taken in connection with the depth of water, the large number of species 

 represented, and the before-mentioned fact that tliere are many fresh- 

 water and fossil as well as marine forms, makes it evident that the 

 entire deposit is (composed of fine detritus gradually sifted down upon 

 the sea bottom and conveyed there by currents from a considerable 

 distance. 



The Delaware Eiver has without doubt supplied most of the mate- 

 rial of this dredging, as it empties into the ocean almost directly west 

 of the locality where it was taken, and as most of the forms (marine 

 and fresh) are such as are common in rivers and streams of correspond- 

 ingly temperate latitude. 



An interesting corroboration of this is to be found in one of the fossil 

 species, Navicula Schultsei Kain. This diatom was originally discovered 

 in material from an artesian well at Atlantic City, N. J,, at a depth of 406 

 feet, by Mr. C. H. Kain, of Pliiladelphia, Pa., and named by him. The 

 same stratum however, outcrops at several places along the Delaware 

 River watershed, notably at Shiloh, N. J., and this diatom, with, perha])s, 

 Raplioneis gemmifcra Bhrb., and Dthcr of the fossil forms, could have 

 gotten into this dredging in no other way than by being brought by the 

 Delaware River from some of these outcrops. But there are some forms 

 occurring abundantly in this deposit which are essentially tropical ; these 



Proceedings National Museum, Vol. XVI— No. 937. 



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