52 Lake Maxinkuckee, Physical and Biological Survey 



that is, the normal or usual shape of the species. The peculiar 

 elongate form of the adult is therefore evidently the product of 

 local influences. The young shells are very iridescent and trans- 

 lucent — much more so than those found in rivers. 



Q. rubiginosa is at its best a very fair button shell, but the 

 lake shells are too small to work up well. This species appears to 

 be rather rare in lakes. The only lake examples of this species 

 with which the Lost Lake shells were compared were some obtained 

 in Lake Erie. The Lake Erie shells were much more dwarfed, but 

 very solid. 



Food: — The following is the result of an examination of the 

 material found in the intestines of Q. rubiginosa from Lost Lake: 



Sample 1. August 2, 1908. Mass fine flocculent rather brown- 

 ish green material, cohering somewhat in cylinders. Looks as if 

 chiefly organic ; not gritty to touch. Organisms present : Scen- 

 edesmus, Fragilaria, Tetraedron, Navicula, Peridinium tabulatum, 

 Anuraea, and Botryococcus braunii. 



Sample 2. August 20, 1908. A large amount of material ; ap- 

 pearance in vial, bottom black, top a fine flocculent sediment. In 

 the top material are Teraedron, Scenedesmus, Microcystis aerug- 

 inosa, and many disassociated minute cells. Black bottom com- 

 posed of Anuraea, Lyngbya aestuarii, a long filament; Scenedes- 

 mus, many, Peridinium tabulatum, Tetraedron, Epithemia turgida, 

 Merismopedia, cast of Cyclops, Melosira crenulata, Gloeocapsa, 

 Staurastrum, Pediastrum boryanum, Gomphonema, Chaetophora, 

 Cosmarium, sponge spicule, Gomphosphaeria aponina, and Botry- 

 ococcus braunii. 



Sample 3. August 20, 1908. A small amount of flocculent 

 brownish material. 



Microcystis aeruginosa, Peridinium tabulatum many and a good 

 many empty cuirasses, Chydorus, Eudorina a few, Scenedesmus 

 common ; Diatoms, Pediastrum duplex. 



Sample 4. August 20, 1908. Fine blue-green flocculent ma- 

 terial. Lyngbya aestuarii, several filaments; Microcystis aerug- 

 inosa, common; Coelosphaerium kuetzingianum, Peridinium tabu- 

 latum, very abundant; Chydorus, Anuraea, Botryococcus braunii, 

 Coelastrum, Staurastrum 1, small, Navacula, several. 



Sample 5. August 20, 1908. Fine bluish-green material. 

 Peridinium tabulatum, abundant; Cymbella cymbiformis, Navi- 

 cula, a few; Anuraea cochlearis, Microcystis aeruginosa, Chydorus 

 1 entire, and other fragments ; Pediastrum duplex, Coelosphaerium 

 kuetzingianum; Cosmarium, Coscinodiscus, Scenedesmus, very 

 common ; Merismopedia glauca. 



