16 THE NAUTILUS. 
ON THE OCCURRENCE OF UNIO COMPLANATUS SOL., IN MICHIGAN. 
BY BRYANT WALKER, DETROIT, MICH. 
The first catalogue of Michigan shells was published by Dr. 
Abram Sager, in 1839. The second by Dr. Manly Miles appeared 
in the “Report of the Geological Survey” for 1860. In each of 
these lists Unio complanatus Sol., is cited as a resident of the State, 
but in neither is any information given as to the exact locality where 
the species had been, or could be, found. In the several catalogues 
which have been compiled since that time, no reference is made to 
the species; and it seems to have been entirely unknown to recent 
collectors, as an inhabitant of the State. 
Such was the condition of things when I gathered together the 
materials for my Catalogue of Michigan Shells, published in 1879 
in the Journal of Conchology (Vol. ii, p. 325). That the species 
was really to be found within our limits seemed, in view of what 
was known of its distribution, very doubtful. It is peculiarly an 
eastern species. Exceedingly abundant in all streams flowing into 
the Atlantic, from Florida to Maine, like its associated species 
Goniobasis virginica Gm., its range westward was known to be very 
limited. It had not been found at all in waters tributary to the 
Mississippi, nor in any of the States bordering on the great lakes 
(excluding Sager & Miles’ citation) west of New York. There was 
no record of its occurrence in any of the great lakes themselves, nor 
in their connecting rivers west of the Niagara river. It did not 
appear to be among the species found by Dr. Gould on the north 
shore of Lake Superior. 
~ In view of all these facts I felt justified in doubting the identifica- 
tion of the specimens referred to this species by Sager and Miles, 
' especially as G. virginica Gm. also appeared in their lists, and with 
entire confidence expressed the opinion that the citation was “evi- 
dently a mistake.” 
Since that time, however, the researches of the Canadian natural- 
ists have shown that the species has a wide range through British 
America, extending as far west as Manitoba. But until within the 
last year, no evidence had been received tending to show a similar 
range through the States south of the great lakes. 
