140 THE AMERICAN MIDLAND NATURALIST 
_ Depvucrions rrom TasLe or PERCENTAGES. 
The greatest increase of any of these dimensions is seen to be in 
DSD and PHL. While an increase is noted throughout the years, 
it is nearly uniform in PD, AD, and DVD, and rather large in TH. - 
Growth is most rapid between 12-16 years, when it is especially 
noticeable in L, DVD, TH, DSD; less so in AHL. 
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9. ANODONTOIDES FERRUSSACIANUS SUBCYLINDRACEOUS 
oO. 
Spec. Age L DVD DSP PD INDY Heil /NEIL Tel. 
2 3 4.78cm. 3. Icm. 1.65cm. 3.67cm. 1. lem. 2.02cm. .93cm. .08cm. 
11% 124% 113% 120% 
34% 133% 134% 137% 
38% 154% 136% 147% 
40% 163% 146% 187% | 
151% 119% 163% 141% 172% 123% 200% 187% 
162% 121% 180% 150% 200% 148% 155% 175% 
Average growth per year in each dimension for 9 years, 
6% 8% 33% 26% 33% 27% 32% 39% 
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Depuctions From TaBLEe or PERCENTAGES. 
Increase with age is most marked in DSD, AD, TH and AHL. 
All dimensions grow more rapidly between 6-9 years than between 
3-6. Increase in height, DVD, is little; growth of L, PD, PHL is 
_ uniform, that of thickness, rapid. This shell is one which is rarely 
found in large rivers. 
10. LIGUMIA, (LAMPSILISP RECTA.) 
Sree Age 1 DVD DSD PD ADVE ARIE so ake 
| 9 6. Iem. 2. 3cm. 1.45cm. 4. 8cm. 1.13cm. 3. lem. 85cm..15cm. 
10 155% 200% 170% 150% 185% 180% 167% 226% 
verage growth per year in each dimension for 18 years, 
7% 12% 81% 59G 714% * 19% 72% 106% 
Depuctions FRoM TABLE OF PERCENTAGES AND REMARKS. 
Within the limits of the ages represented, it seems clear that DVD, 
DSD, PD, PHL, and AHL increase most rapidly with age. The 
rate is greater in TH; L and AD have apparently the same rate 
of growth, while the remaining dimensions, with the exception of TH, 
