263 



ably deeper in the sand than the older shells, they are harder to find. 

 These half-grown shells are of a peculiarly beautiful golden yellow 

 color with a satiny epidermis, and are of the same shape as those found 

 in the neighboring rivers, 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 translucent, much more so than those found in rivers. 



Q. ruhiginosa 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 are much more dwarfed, but very solid. 



Food. 



The following is the result of an examination of the material found 

 in the intestines of Q. ruhiginosa from Lost Lake. 



Sample 1. August 2, 1908. Mass fine flocculent rather brownish 

 green material, cohering somewhat in cylinders; looks as if chiefly 

 organic; not gritty to touch. Organisms present: Scenedesmiis, Fra- 

 gilaria, Tetraedron, Navicula, Peridinium tabulatimi, Anursea, and Bo- 

 tryococcus braunii. 



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

 ance in vial: bottom black, top a fine flocculent sediment. In the top 

 material are Tetraedron, Scenedesmus, Microcystis seriginosa and many 

 disassociated minute cells. Black bottom composed of Anursea, Lyngbya 

 xstuarii, a long filament; Scenedesmus, many Peridinium tabulatum, 

 Tetraedron, Epithemia turgida, Merismopoedia, cast of Cyclops, Melo- 

 sira crenulata, Glceocapsa, Staurastrum, Pediastrum boryanum, Goni- 

 phonema, Chsetophora, Cosmarium, sponge spicule, Gomphosj}}iseria 

 aponina, and Botryococcus 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 material. 

 Lyngbya sestuarii, several filaments; Microcystis seruginosa, common; 



