46 Lake Maxinkuckee, Physical and Biological Survey 



winter of 1900-1901 an example of Lampsilis hdeola, in rather 

 deep water in the vicinity of Winfield's, was observed to have 

 moved about 18 inches within a few days. Its track could be dis- 

 tinctly seen through the clear ice. 



As a result of the quiescence of the lake mussels, the posterior 

 half or J of the shell, which projects up from the lake bottom, is 

 usually covered by a thick marly concretion which appears to be 

 a mixture of minute alga^ and lime. This marly concretion grows 

 concentrically, forming rounded nodules, its development increas- 

 ing with the age and size of the shell. This concretion, though 

 most abundant on shells, is not confined entirely to them, but grows 

 also on A"ocks that have lain undisturbed on the bottom. When 

 growing on shells, it adheres to them very closely; and upon being 

 pried loose sometimes separates from them much as the matrix 

 separates from a fossil, and leaves the epidermis of the mussel 

 clean. In other cases it adheres more firmly and is difficult to 

 scrape off clean. On this marly growth, colonies of Ophrydium, 

 much the size, color, and general appearance of grapes with the 

 skins removed, are often found growing, and in the cavities and 

 interstices of the marl, a handsome little water-beetle, Sfenelmis 

 tmdulatus B\s(.tch\ey, and its peculiar elongate black larvse, live in 

 considerable numbers but apparently have nothing to do with the 

 mussels. Various species of hydrachnids, one of them strikingly 

 handsome with its green body sprinkled with bright red dots, also 

 live in the cavities of the marl, and offer some suggestion as to 

 how the parasitic mite Atax went a step farther and took up its 

 habitation within the mussel itself. 



Food and feeding: — An examination of the stomach and in- 

 testinal contents of the various species of mussels of the lake 

 showed no noticeable differences between the food of the different 

 species. Enough of the bottom mud is generally present to give 

 the food mass the color of the bottom on which the mussels are 

 found; thus the stomach-contents of the mussels found in the 

 black bottom of Lost Lake was usually blackish, while that of 

 those found in the lighter bottom at Long Point was grayish. In- 

 termixed, however, with the whole mass was always enough algse 

 to give it a somewhat greenish tinge, this green being usually inter- 

 mixed more or less in the form of flakes. A striking contrast be- 

 tween the stomach contents of mussels inhabiting lakes and those 

 found in rivers is the much greater preponderance of organic mat- 

 ter in the food of the lake mussels. The stomach contents of river- 

 mussels is generally chiefly mud, with a few diatoms, desmids, 

 Scenedcsmus and Pediastrum intermixed, as said above. Those of 



