48 Lake Maxinkuckee, Physical and Biological Survey 



important, agents in separating the lime from the water, is quite 

 certain. Chief among these agencies are the various mollusks, 

 especially the Unionidse and Vivipara contectoides, and certain 

 plants, such as the Charas and Potamogetons. These have the 

 power of separating out from the water the soluble calcic com- 

 pounds and converting them into insoluble compounds which con- 

 stitute the basis of the marl. 



The most abundant and most widely distributed mollusk in 

 the lake is the univalve, Vivipara contectoides. This rather hand- 

 some and beautifully marked shell occurs throughout the lake, 

 apparently at all depths and on all kinds of bottom, but it is most 

 noticeable in the great windrows of dead shells that are so often 

 seen lining the beach, particularly at low water. These mollusks 

 evidently die by the million every year. Their shells are fragile 

 and disintegrate rapidly. The total annual limy accumulation on 

 the lake bottom from this source alone must be quite considerable. 



Next to Vivipara contectoides is the species of mussel known as 

 fat pocket-book, Lampsilis luteola. As set forth elsewhere in this 

 report, this is the most abundant species of freshwater mussel in 

 the lake. It is pretty generally distributed and is very abundant. 

 There are several very extensive beds, particularly off Long Point 

 and in the south end of the lake. Then there are at least 13 other 

 species of mussels and no fewer than 30 or 40 species of gastero- 

 pods, some of them represented by myriads of individuals. Be- 

 sides such of the mussels as naturally die, the muskrats make 

 considerable onslaughts upon them, leaving their shells strewn 

 over the bottom to decay, and millions of the gasteropods die every 

 year, and their decaying shells go to augment the lime deposited 

 in the bottom of the lake. And there are several species of plants 

 which have the power of separating the lime from the water. The 

 most notable of these are the various species of Chara, some of 

 which are so heavily encrusted in lime that when dried out on shore 

 they become a chalky brittle mass and are accordingly known among 

 fish-culturists as "lime-plants". These grow in depths up to 15 

 or 20 feet, and most of the plants grow in thick carpets on the 

 bottom, the older portions becoming so thickly encrusted that they 

 are hardly recognizable. 



Besides the Charas there are not fewer than 14 species of pond- 

 weed or Potamogeton, all of which, in varying degrees are lime 

 gatherers. Their leaves, particularly those of Potamogeton ampli- 

 folius, P. compressus, P. robbinsii and P. americanus, are often 

 encrusted with lime, the first mentioned species so heavily that the 



