XXVII.-SKETCH OF THE LWERTEBRATE FAUNA OF LAKE 



SUPERIOR. 



By Sidney I. Smith. 



In tlie following paper, I have attempted to bring together all the 

 species of invertebrate animals, excepting many aquatic insecDs and 

 some groups of minute forms, known to inhabit the waters of Lake Su. 

 perior. I had at first intended to make it a sketch of the invertebrate 

 fauna of the entire chain of the great lakes, but found it impossible to 

 bring together material enough for that purpose, and so have limited 

 myself to the immediate region of Lake Superior. One of the principal 

 objects of the article is to furnish a means of comparing the food of the 

 fishes with the fauna of the waters which they inhabit. For this pur- 

 Xiose, the 'fauna of Lake Superior is of more importance than that of the 

 other lakes, since most of the material which I have examined from the 

 stomachs of the lake-fishes was obtained in that lake by Mr. J. W. 

 Milner. This account is undoubtedly very imperfect in all the groups; 

 and some species which have been recorded as inhabiting the lake are 

 very likely omitted, although I have intended to include all such. Of 

 the insects I have attempted to mention only a very few species which 

 are important as food for the white-fish, or interesting on account of the 

 bathymetrical distribution. Most of the copepod and ostracoid Crustacea 

 of the region are omitted, since they have not as yet been sufficiently 

 studied by any one. 



The account of the fauna of the depths of the lake is based almost 

 entirely on a series of dredgings made during August and the early part 

 of September, 1871, under the direction of General 0. B, Comstock, 

 superintendent of the survey of the northern and northwestern lakes 

 and rivers. A preliminary report of these dredgings was made to Gen- 

 eral Comstock in October, 1871, and published as Appendix K in the 

 Report of the Chief of Engineers, forming the second volume of the Re- 

 port of the Secretary- of War for 1871. Comparatively few of the shore- 

 species were collected on this excursion, and consequently some parts 

 of this paper have been largely compiled from other sources, especiallj^ 

 from Professor Agassiz's work on Lake Superior. In all cases where the 

 facts were not obtained by myself, however, I have given the authority 

 on which they are inserted. 



In order that the references to localities and depths may be better un- 

 derstood, I give a short account of the dredgings conducted by the lake- 

 survey. The dredgings were all made by hand from the steamer Search, 

 while employed in oif shore sounding, or in transporting shore-parties. 

 The dredges used were like those commonly employed in marine dredg- 



