60 Lake Maxinkuckee, Physical and Biological Survey 



1 young Atax in gill; Cotylaspis insignis in axil of gill. Food 

 chiefly Microcystis aeruginosa, a little Botryococcus braunii, Lyng- 

 bya aestuarii and Pediastrum boryanum. 



6. PAPER-SHELL 



ANODONTA IMBECILLIS Say 



A single specimen. 



7. SQUAWFOOT 



STROPHITUS EDENTULUS (Say) 



Not very common in the lake. Occasional shells can be picked 

 up along shore, especially between Long Point and Arlington, and 

 along the north shore. Living examples were also taken in small 

 numbers from the mussel bed at the mouth of Norris Inlet, and at 

 Long Point. In a collection of about 300 living mussels collected 

 at the latter place in the autumn of 1907, only 3 were of this 

 species. 



As found in the various rivers of the country, this is one of the 

 most variable of shells, and the exact limits of the species and its 

 various forms are not yet well worked out. The lake examples, 

 though differing considerably from those of the neighboring rivers 

 and from river shells in general, do not exhibit a very large range 

 of variation. They are all markedly dwarfed, the average length 

 being about 2^ inches or 63.5 mm. long. All have a well-developed 

 rounded posterior ridge. The epidermis is deeply stained, that of 

 the exposed portion of the shell being a rich yellowish brown, 

 while the anterior portion in the living shell buried in the soil 

 of the bottom is a deep, shining, brown black. The anterior mar- 

 gin is not nearly so heavy and produced as one frequently finds 

 it in river examples. The beaks of the lake shells are not so angu- 

 lar as they usually are in river shells, and the high wavy ridges 

 are more numerous and pronounced. In the Maxinkuckee shells, 

 also, a number of fine hair-like lines or ridges, much like growth 

 lines, extend along the posterior border of the umbone, parallel 

 with the posterior ridge of the earlier stages of the shell. 



The nacre of the lake shells is a rich rosy salmon. Unlike 

 the salmon color of "Anodonta salmonia" this is a natural color, 

 not due to diseased conditions; the nacre surface is very smooth 

 and the color extends deeply into the shell. In some cases the 

 inner nacreous surface appears to be a secondary thickening of 

 the shell, laid on the older portions like an enamel. Below this 

 extra nacreous deposit the growth lines are very distinct on the 



