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[From the American Journal of Science and Arts, Vol. II, Nov., 1871.] 



5. Dredging in Lake Superior under the direction of the JJ. J8. 

 Lake Survey. — Extensive dredgings were undertaken the past sea- 

 son in Lake Superior, from the IT. S. steamer Search, under the di- 

 rection of Gen. C. B. Comstock, Superintendent of the Lake Survey. 

 Dredging was carried on from the shallow waters, especially 

 along the north shore, down to 169 fathoms, the deepest point 

 known in the lake. In all the deeper parts of the lake, the 

 bottom, as shown both by the dredging and by the soundings 

 executed by the Survey, is covered with a uniform deposit of 

 clay, or clayey mud, usually very soft and bluish or drab in 

 color. Water brought from the bottom at many points was per- 

 fectly fresh ; that from 169 fathoms gave no precipitate with 

 nitrate of silver. The temperature, everywhere below 30 or 40 

 fathoms, varied very little from 39°, while at surface (at the time 

 of the observations, during August) it varied from 50° to 55°. 

 The fauna of the bottom corresponds with these physical condi- 

 tions. In the shallow waters, the species vary with the varying 

 character of the bottom, while below 30 to 40 fathoms, where the 

 deep-water fauna properly begins, the species seem to be every- 

 where very uniformly distributed. The deep-water fauna, as 

 might be expected from the unfavorable character of the bottom, 

 is meager, and seems to be characterized rather by the absence of 

 many of the shore species than by forms peculiar to itself. Some 

 of the more interesting species occurring in deep water were : 

 My sis relicta Loven, at various depths from 4 to 159 fathoms; 

 Pontoporeia affinis Lindst., at nearly every haul from the 

 shallowest to the deepest ; a small undescribed species of 

 Pisidiurn, down to 159 fathoms; several forms of dipterous 

 larvre, allied to Ghironomus, down to the same depth ; several 

 species of Lumbricoid worms, of the genera Tabifex, Scenuris, 

 and an allied genns ; and a species of Hydra, which was found 

 from the shore down to 159 fathoms. Of these, the My sis, Ponto- 

 poreia, and Pisidiurn are identical with species found by Dr. 

 Stimpson in his dredging in Lake Michigan, a short account of 

 which was published in the American Naturalist for September, 

 1870. The species of My sis and Pontoporeia I am unable to 

 distinguish from specimens from Lake Wetter in Sweden. In the 

 Swedish lakes, these species were associated with Ldotcea entomon 

 and Gammar acanthus loricatus, marine species, and were supposed 

 by Loven to have been derived from ancient marine species left 

 in the lake basins by the recession of the ocean. The occurrence 

 of these forms in Lake Superior, so far removed from the ocean, 

 is certainly a very interesting fact in the geographical distribu- 

 tion of species, but one which I will not attempt to discuss in 

 this brief notice. In the shallow waters many interesting species 

 were obtained. Among these was a new species of Grangonyx, a 

 genus closely allied to Gammarus, and heretofore known only 

 from a few species found in the fresh waters of the old world, 

 which occurred in 8 to 13 fathoms; and at the same depth, species 

 of Lumbricus, Nephelis, Procotyla, Gammarus, Asellus, Limncea, 

 Physa, Planorbis, Valvata, Sphcerium, Pisidiurn, etc. A full 

 report will soon be published. s. i. smith. 



