320 Miscellaneous. 



near T. TJiompsonii. If this prove so on further investigation, it 

 will be named Tnglopsis Stimpsonii What is peculiarly interesting 

 about this small fish is, that it is a salt-water rather than a fresh- 

 water form. Judging from the quantity of fragments belonging to 

 this species obtained from the stomachs of trout caught in the deep 

 water, it must be by no means rare, 



I submitted the minute crustaceans to Dr. Stimpson, who detected 

 three species of freshwater shrimps belonging to the genus Gamma- 

 rus, and one species of Mysis, a marine genus, many species of which 

 are found in the North Atlantic and Arctic oceans. The small 

 shell found with the crustaceans, in the stomachs of the whitefish, 

 proved to be an undescribed species of Pisid'mm. 



These discoveries were considered of sufficient importance to justify 

 the undertaking of a dredging-expedition. Professors Stimpson and 

 Andrews, with Mr. Blatchford, of Chicago, represented the Chicago 

 Academy of Science, while Drs. Lapham and Hoy represented the 

 Wisconsin Academy of Arts and Letters. 



On the 24th of June, 1870, we steamed into the lake, out of sight 

 of land, and spent the entire day in dredgimj in a most enjoyable 

 and, to science, profitable manner. We procured living specimens of 

 those crustaceans which I had previously obtained from the stomachs 

 of whitefish. But, with every exertion, wc were not able to keep 

 them alive above a few hours. Fitted, as they are, to sustain the 

 great pressure of from fifty to seventy fathoms of water, when this 

 was taken off, death was the inevitable result. 



I here subjoin a catalogue of all the animals thus far known to 

 inhabit the deep water off" Racine : — 



Ganimarus Hoyi, Stimpson. 



brevistilus, Stimpson. 



filicornis, Stimpson. 



Mysis diluvianus, Stimpson. 

 Pisidium abyssorum, Stimpson. 



Salmo amethystus, Mitchel. 

 Coregonus sapidissimus, Agassiz. 



latior, Agassiz. 



Argyrosomus Hoyi,6V//. 



nigripinnis, GiU. 



Triglopsis Thompsonii, G'trarc?. 



Also one species of parasitic leech, found fastened to whitefish, 

 and a small white Planaria. 



In conclusion, the occurrence of marine forms {Mysis and Tn- 

 glopsis) goes far to prove that Lake Michigan was once salt — had 

 direct communication with the ocean. As it gradually became ele- 

 vated above the sea, it would naturally take many years to expel the 

 salt water, especially as its greater specific gravity would cause it to 

 sink and remain long in the lake — time sufficient for the animals to 

 become acclimated to the changed condition of things. It is barely 

 possible that salt springs at the bottom of the lake may have mate- 

 rially retarded the change, and that even now there may be brackish 

 water in the greatest depths. This seems the more probable, since 

 the salt-bearing strata occur in Michigan. We made an efibrt to 

 solve the query ; but, owing to the imperfection of the apparatus, I am 

 not certain that the negative was proved. — Trans. Wisconsin Acad. 

 Sci. ^c. 1870-72, pp. 98-101, 



