ANNUAL GROWTH OF FRESH-WATER MUSSELS 
735 
The values obtained for these two species have been incorporated in Figure 19 
and Tables 13 and 14 for the buckhorn; and Figure 20 and Table 15, for Pope’s 
purple. 
Table 14. — Weight in relation to age of buckhorn , Tritogonia verrucosa (Rafinesque ) , Mississippi 
River, Iowa. 
Ring 
Weight 
VIII 
Grams 
20. 1 
40.3 
IX 
X 
XI 
54.8 
CMS. 
i r 
UNIO POPEI 
] 
□ 
RIO G 
LENGTH 
ON 
TANDE VALLEY. TEX 
a 
AG 
> 
J 
□ 
Sq 
WEIGHT 
ON 
1Kb 
L_J 
m 
VRS. RINGS 1 II 01 IV V VI 
GMS 
100 
80 
60 
40 
20 
Figure 20.— Bar graph showing length (left) plotted against age, and weight 
(right) plotted against age of seven individual right valves of Pope’s purple 
from Rio Grande near Mercedes, Tex. 
Table 15 . — Males and females, Pope’s purple, Unio popei, Lea, Rio Grande Valley, Tex. 
Age in years 
Weights 
Length 
Height 
One- 
half 
ventri- 
cosity 1 
Annual rings 
Left 
valve 
Right 
valve 
Mean 
I 
II 
III 
IV 
V 
VI 
3 
Grams 
( 31. 4 
| 44.9 
64.5 
88.7 
Grams 
29.9 
34.9 
41.3 
45.0 
41.6 
64.0 
89.3 
32.4 
42.6 
64.0 
89.3 
Centi- 
meters 
8. 41 
8. 55 
9. 13 
9. 32 
9. 92 
10. 82 
11.79 
Centi- 
meters 
5. 50 
5. 65 
6. 02 
6. 35 
6. 95 
7.38 
8. 17 
Centi- 
meters 
1.91 
1. 94 
2.01 
2. 19 
2. 13 
2. 45 
2. 86 
3.29 
3. 66 
3.08 
3. 13 
3. 78 
3. 05 
3. 52 
6.71 
6.51 
6. 08 
6. 20 
6. 92 
6. 63 
6. 80 
8. 41 
8. 55 
7.85 
8. 16 
8. 62 
8.61 
8. 81 
4 
5 
6 
9. 13 
9. 32 
9. 92 
9. 92 
9.91 
10. 82 
10. 70 
"’ll.’ 79 
1 By ventricosity is understood the greatest thickness of the two valves when closed, measurement usually falling in the umbonal 
region. 
As it is not intended to give a detailed study of these species here, they are 
reviewed together. It was found that the ring method was quite as satisfactory 
for the study of these species as for Lampsilis anodontoides and Lampsilis siliquoidea 
pepinensis, and that the same type of growth curves were obtained in all cases. 
Comparisons within the species show that the rate of growth of the yellow sand 
shell was greater in the southern and middle portions of its range than in the northern 
