MUSSEL FAUNA OF THE KANKAKEE BASIN. 37 



The two upper basins are remarkably free from aquatic vegeta- 

 tion, while Oswego basin is packed with Potamogeton^ Utricvlaria, 

 Philotria^ and many species of rushes, spatter-dock, water arum, 

 pickerel weed, cat-tails, etc. 



The entire lake is surrounded by high and steep banks except in 

 <one or two places, and promontories run out into it from both sides. 

 At the southernmost of these promontories on the east side the 

 lake has the remarkable depth of 178 feet, making it probably the 

 deepest fresh-water lake of its size in America. And this is true 

 of the whole lake, the only shallow-water areas of , any size being the 

 delta brought in by the Tippecanoe River and a small area along 

 the north side of the east shore. Furthermore, the lake is to-day 

 more nearly in its natural state than any of the others examined. 

 It was a genuine relief to find such a body of water unaffected by 

 damming or draining. 



Owing to its great depth, the water is always cool, even in the hot- 

 test weather, and is very clear and free from vegetable debris. The 

 bottom is hard and marly in most places except the Oswego Basin, 

 where it is soft black muck. The entire margin of the lake and 

 Tippecanoe River for a mile and a half below the outlet were ex- 

 amined, and mussels were everywhere abundant. At Government 

 Point, over the shallow-water area on the eastern margin already 

 mentioned, they were especially plentiful. Here the marly bottom 

 was softer and the mussels had dug circular cavities 2 or 3 inches 

 deep into the marl. In the bottom of the excavation were some- 

 times one mussel, sometimes a whole nest of them of varying sizes. 

 Anodonta, Strophitus, and Lampsilis were thus found. 



This and other portions of the eastern shore were the only places 

 where L. glans and M. fahale were found during the entire summer, 

 wdth one exception for each species. 



In the Tippecanoe River the sand and gravel of the swifter cur- 

 rent and the marl of the quieter water were found thickly covered 

 everywhere with living mussels and dead shells. Q. undulata was 

 the most common species and most of the specimens were excep- 

 tionally large and plump. In several of them there was a decided 

 breaking up of the ridges on the outside surface into pustules simi- 

 lar to those on pvstulosa, making a sort of nondescript shell that 

 was difficult to classify at first. 



As would be expected, there were a few species in this fauna not 

 found in the Kankakee Basin. These include Micromya fahale, L. 

 Tnultiradiatus, T . sulcata, and P. phaseolus. 



The Quadrulas have been searched strenuously for pearls and sev- 

 eral good ones are reported to have been found, but none of the 

 other species contain either pearls or baroques. 



9275°— 13 13 



