lod 
THE NAUTILUS. 17 
In the summer of 1888, Dr. M. L. Leach of Traverse City, 
Michigan, while exploring Ocqueoe Lake in Presque Isle County, 
Michigan, found a Unio in abundance, which proves to be U. 
complanatus. His account of this “find” is as follows: 
“Tn a nameless brook that drains a small lake into the Ocqueoe 
from the north, I found great numbers of the Unio referred to. You 
know I had hopes of finding a ‘ giant clam shell,’ and shell heaps 
made by some primitive people in the Ocqueoc. I found the heaps, 
which are only beds of shells, not more than six inches in depth, 
and seldom more than two or three square yards in area, scattered 
irregularly about over a few square rods of ground. They are on 
dry land a few rods from the brook, are very old, and are evidently 
the refuse from the camps of some primitive people who ate the 
clams. I could find in them only the one species of Unio, now exist- 
ing in the brook. Smaller collections of refuse shells are seen at 
other points on the banks of the lake, but all consisting exclusively 
of this one Unio. So much for a sensational newspaper story.” 
These facts show that the colony ot U. complanatus thus dis- 
covered is one of ancient origin, though apparently of limited extent. 
How it came to be there is a very interesting question. The very 
considerable labors of our collectors in other parts of the State, 
especially through the southern and western portions, have failed to 
discover the species elsewhere. The existence of this isolated colony, 
far from any other known locality where it is found, is one of those 
peculiar facts of distribution which arrest the attention, and 
challenge investigation. It may be considered practically assured | 
that the species does not occur in the southern portion of the State 
which has been most thoroughly worked over. Should future explora- 
tions find the species inhabiting the streams of the upper peninsula 
and the more northern counties of the lower peninsula the explana- 
tion would be obvious. But until that is known, all is conjecture, 
except the fact that the species does inhabit the Ocqueoe and its trib- 
utaries and is entitled to admission to the fauna of Michigan. 
DESCRIPTION OF HELIX (TRACHIA) DENTONI N. SP. 
BY JOHN FORD, PHILADELPHIA. 
Shell small, depressed, umbilicate, rather thin, shining; color 
corneous-brown, encircled above the periphery by a faint brown 
