MUSSEL FAUNA OF THE KANKAKEE BASIN. 



47 



Anodontas are always more subject to attacks of parasites than any 

 other of our fresh-water mussels, and those of the Kankakee Basin 

 were no exceptions to this rule. Common among the parasites is a 

 distomid which usually is found on the surface of the mantle in the 

 dorsal region of the mussel next to the hinge and causing the nacre 

 to become brick red in color. As this distomid has never received 

 a scientific name, the adult form being up to the present unknown, 

 in our reference to it we have spoken of this form as the distomid 

 of Osborn, after its discoverer. Others of the infected shells were 

 of a dark chocolate color and the distomids, which were plentiful, 

 were smaller in size and probably belonged to a different species. 



Other parasites frequently found were Aspidog aster conchicola 

 in the pericardial cavitj^, Cotylaspis insignis in the axils of the 

 gills, and numerous species of Atax inhabiting the branchial cavity. 

 All the Anodontas found in the streams corresponded pretty closely 

 to one type, in no case departing so far as to raise any doubts as to 

 identity; in the lakes, however, it was different; each lake seemed 

 to have a more or less pronounced type of its own. The Anodontas 

 of Twin Lakes resemble those of Bass Lake and Cedar Lake pretty 

 closely, but those of Lake of the Woods differ considerably, being 

 larger and thinner. At Tippecanoe Lake, where the dead Anodonta 

 shells were so abundant that in places we would frequently find them 

 nested sometimes three in a nest, they presented a different, more 

 inflated type. They very closely, indeed, approached the form known 

 as Anodonta corpulenta^ generally considered a distinct species from 

 grandis. We also found two broken dead shells at Tippecanoe Lake 

 which very closely resembled A. siiborbiculata^ and may, indeed, have 

 been that species ; more material would be desirable before deciding. 



The Anodontas from one of the Twin Lakes, as has already been 

 remarked, were infected in great numbers by a distomid forming 

 clear spherical cysts in the margin of the mantle. Sporocysts and 

 peculiar large white areas like blisters were common on the Anodon- 

 tas of Tippecanoe Lake. 



W. Anodonta imhecillis {Say), — This dainty, fragile Anodonta is 

 of no commercial value. It is a shell of ponds and small streams. 

 The only shell found in Millpond Lake of the Twin Lakes was one 

 example of this species. In the Yellow Kiver at Plymouth below the 

 : dam it was fairly common. On July 14 several were obtained here, 

 all gravid, the entire outer gills being thick and padlike, and, when 

 I the gills were fully ripe, dark brown. The glochidia have a brown 

 I shell, shield-shaped in profile, and have long, coiled threads. One 

 I found in Tippecanoe Lake was unusually elongate. A large one was 

 ' found m the Yellow Kiver at Zinc Bridge, another was found in 

 I the outlet of Fish Lakes, and a gravid example was found in the 

 Kankakee bed at Davis (Aug. 9). 

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