i6o 



College of Foreslry 



from shallow water being more typical, cjuadrate, while those 

 from deeper water are more cylindrical. Shallow water indi- 

 viduals also have cleaner shells with brown epidermis, fre- 

 quently strongly rayed anteriorly. Individuals inhabiting 

 deeper water, especially on a mud bottom, are strongly en- 

 crusted with lime and the shells are dull black. A large 

 percentage of small specimens (20-30 mm. long) from all 

 depths have a green shell with dark rays. The interior of 

 nearly all shells is pvu-plish with either a coppery shade or 

 with many copper spots, usually rounded in form. The differ- 

 ence in size between shallow water and deeper water individ- 

 uals is shown in the table below: 



Table No. 48. Variation in Size of Elliptio Complanatus 



Length 70, height 

 Length 70, height 

 Length 66, height 

 Length 72, height 

 Length 60, height 

 Length 59, height 

 Length 63, height 

 Length 56, height 



38, breadth 18 mm., 

 35, breadth 22 mm., 

 35, breadth 20 mm., 

 40, breadth ig mm., 

 32, breadth 17 mm., 

 31, breadth 16 mm., 

 35, breadth 18 mm., 

 31, breadth 14 mm., 



5-6 feet deep, 



5-6 feet deep, 



5-6 feet deep, 



2-3 feet deep, 



18 feet deep, 



18 feet deep, 



15 feet deep, 



15 feet deep. 



sand bottom, 

 sand bottom, 

 sand bottom, 

 sandy clay, 

 mud bottom, 

 mud bottom, 

 gravel-sand, 

 gravel-sand. 



All individuals of this species from the lake are smaller on 

 the average than examples from other localities. Several 

 gravid females were noted (July) and young shells from 3 to 

 20 mm. long were observed. These occurred at various depths 

 and on different kinds of bottom, as noted in the table below : 



Table No. 49. Distribution of Juvenile Elliptic 



