692 EEPORT OF COMMISSIONER OF FISH AND FISHERIES. 



the main island and a smaller one, and due south of Saint Ignace 

 station, September 4, two hauls, 8 and 10 to 13 fathoms, a little sand 

 and mud brought up with great quantities of the same species of 

 alga found at Simmon's Harbor, and which, according to Prof. D. C. 

 Eaton, who kindly examined it for me, is a small, densely-tufted species 

 of Cladophora, possibly G. glomerata Linn., a most variable species, but 

 the specimens do not well correspond with authentic ones from Ger- 

 many. This alga was brought up in immense quantities, the dredge 

 being full at each haul. 



On a line between Michipicotoa Island and Copper Harbor, and about 

 thirty-seven miles from the island, September 7, 147 fathoms, soft clay. 



From this list it is readily seen that, in all the deeper parts of the lake, 

 the bottom is covered with a uniform deposit of clay or clayey mud. 

 All the soundings made by the lake-survey show the same thing, the 

 specimens of the bottom brought up from deep water by the lead being 

 everywhere of the same character, varying only in color and somewhat 

 in the amount of sand mixed with the clay. The color was not uniform 

 even in the same dredgeful; drab and bluish masses of the clay being 

 frequently mixed with brown or reddish lumps. In deep water, drab and 

 bluish were the prevailing tints, however. Water was taken from the 

 bottom at many points, and was everywhere perfectly fresh. That from 

 169 fathoms gave no precipitate with nitrate of silver. 



The temperature, everywhere below 30 or 40 fathoms, was very uni- 

 form, varying only slightly from 39°, while at surface, during the season 

 at which the dredging was carried on, it varied from 50^^ to 55°. 



The fauna of the lake-bottom corresponds with these physical condi- 

 tions. In the shallow waters along the shores, the fauna varies with the 

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

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

 everywhere nearly uniformly distributed down to the deepest points. 

 The soft clayey bottom is, however, very unfavorable to most forms of 

 animal life, and, as we might expect, the fauna of this region is very 

 meager. Except among the worms, it seems to have scarcely any species 

 peculiar to it, and is characterized rather by the absence of many of the 

 shallow-water species than by forms peculiar to itself. 



Besides the dredgings made by the lake-survey, Mr. J. W. Milner 

 dredged, in 1872, in GO fathoms off Outer Island, and obtained several 

 of the species which had been found the year before. 



It is proper that I should make a special acknowledgment to Professor 

 Yerrill for the assistance he has given me in the preparation of this 

 paper. The account of the worms in the preliminary report referred to 

 was prepared wholly by him, and in the following pages the enumera- 

 tion and description of the species of that class, with which I am unac. 

 quaiuted, has been made up wholly from his published papers and 

 manuscript notes. Special acknowledgments to Messrs. Temple Prime 

 and Charles M. Wheatley for assistance in determining some of the species 

 of MoUusca will be found under that group. 



