284 Dr. II. A. Nicholson on Dredgings in Lake Ontario. 



results obtained in these dredgings in Lake Ontario agree 

 very fairly with those obtained in Lake Superior ; and there is 

 a general conformity in the phenomena observed. The fauna 

 of Lake Superior, however, so far as deep water is concerned, 

 is decidedly richer than that of Lake Ontario ; whilst some 

 of the more remarkable forms discovered in the former appear 

 to be altogether absent in the latter. This is especially notice- 

 able as regards the singular Stomapod Crustacean Mysis re- 

 licta, which was found in great plenty in Lake Superior at all 

 depths up to 148 fathoms, but which was not detected at all 

 in Lake Ontario. 



As might have been expected upon h jyrion grounds, the 

 fauna of Lake Ontario is not extensive, though some forms 

 occur in great profusion. The shallow-water fauna is very 

 rich in individuals, and the number of species is quite con- 

 siderable for fresh water. No doubt, also, the list might be 

 much increased by a careful examination and by a more extended 

 investigation than it was in my power to carry out. Beyond 

 8 or 10 fathoms the fauna becomes very scanty ; and when we 

 reach depths of 20 fathoms and upwards, the list becomes 

 reduced to some small Annelides and Amphipod Crustaceans. 

 The nature of the bottom, also, at great depths is exceedingly 

 unfavourable to animal life, consisting almost everywhere of a 

 fine clayey mud, the temperature of which is very low. 



The most interesting forms of life discovered were the An- 

 nelides and Crustaceans. The Annelides are very abundant 

 and varied, the two orders of the Hirudinea and OligocJia'ta 

 being both -represented, and the former presenting some species 

 of peculiar interest. Of the Crustacea the most interesting is 

 tlie little Amphipod whicli occurs in such numbers in depths 

 of from 30 to 45 fathoms, and which appears to be identical 

 with the Pontoporeia affinis of the Swedish lakes. This 

 species and the Stomapod Mysis relicta, Loven, are found in 

 Lakes Wetter and Wener in Sweden ; and it is well known 

 that their occurrence in this locality, along with other species 

 of marine genera, led to the belief that these lakes had been 

 formerly part of the sea, from which they had been cut off by 

 geological changes. On this theory these Crustaceans are the 

 survivors of the original marine fauna of the area, whicli had 

 been able to bear up under the gradual changes by which the 

 formerly existing sea was converted into fresh water. The 

 occurrence, therefore, of these same forms of Pontojjoreia and 

 Mysis in Lake Superior and of the former of tlicm in Lake 

 Ontario is an extremely interesting fact, whether Loven's 

 theory is to be accepted or not. It may be mentioned also 

 that there are no insuperable geological diliiciiities wliich 



