Habits and structure of Cotylaspis insignis Lrrpy. 903 
and gave good results for the muscles, but I did not succeed in 
demonstrating the nerves with it, during the experiments I was 
able to make. 
b) Distribution. 
Lake Chautauqua is one of the long and narrow “glacial Lakes”, 
it is about twenty-five miles long and from one to two miles wide. 
It is at the head of a small river which is one of the tributaries 
of the Allegheny river, and is thus one of the head waters of the 
Mississippi River system. It is however only nine miles from Lake 
Erie of the St. Lawrence River system. There are a number of 
summer resorts on the shore of this lake greatest among them 
The Chautauqua Assembly, near the head of the lake, with a 
temporary population of from fifteen to thirty thousand people. The 
city of Jamestown is located at the foot of the lake. Material was 
collected at different points in the lake and from various kinds of 
bottom, but only close to the shore in shallow water. Several 
species of Unionidae are found in the lake: off the Assembly grounds 
we find Anodonta plana Lea and less often A. grandis, Unio luteolus 
Lam. is the commonest species of Unio, while U. edentulus Say is 
very common, and U. ventricosus, U. phaseolus Hrup. and U. gibbosus 
Bar. are found more rarely. I examined a great many individuals 
of all of these species during the years of 1895, 1896, 1897 and 
1898, chiefly from the shore at Chautauqua Assembly, and as a 
general result can say that Cotylaspis occurs in all parts of the lake 
and that it is almost totally confined to Anodonta, being found in 
Unio only in two instances (in U. luteolus). For the sake of a record 
I will state here that my specimens were obtained at the following 
points on the lake: near the head of the lake at Point Chautauqua 
and Chautauqua Assembly, in the middle of the lake at Long Point 
and Bemus Point, and at the foot of the lake at Celoron. I also 
collected at the beginning of the “outlet”, and in the river at 
Jamestown. 
The preference of the fluke for Anodonta is surprising, since 
U. luteolus is equally abundant and U. edentulus also is very frequent. 
At one time I thought that it might be attributed to the fact that 
in Anodonta the kidney is directly accessible from the branchial 
chamber, while in Umno luteolus it is not, since the inner gills 
coalesce with the adjacent surface of the visceral mass. But the 
same communication as in Anodonta exists in U. edentulus, so that 
