728 
BULLETIN OF THE BUREAU OF FISHERIES 
The manufacturers agree that shells which have just reached a “fair commercial 
size” are the most satisfactory for use in the production of buttons. The smaller 
shells, if they be large enough to justify handling and the general overhead of pro- 
duction, are more valuable than the larger shells, which are likely to be more difficult 
to cut without chipping, and which yield blanks so thick that considerable grinding 
down is required. As the term “fair commercial size” is relative, an effort has been 
made to define this size for purposes of comparison. In view of various observations 
made by the manufacturers themselves, the fair commercial size for the yellow sand 
shell seems to be a shell about 10.5 centimeters (approximately 4 inches) in length, 
with a thickness at a point on the pallial line (v. i.) of 0.30 centimeters (0.12 inches, 
or about 5 lignes), and weighing 42 grams (about 1% ounces). With this somewhat 
arbitrarily defined size as a standard, Table 9 has been prepared to determine the 
time required in each of the three localities for the yellow sand shell to reach a fair 
commercial size. At Fairport, Iowa, both males and females required 5 years or 
more; at Newport, Ark., only 4; while in the Rio Grande Valley, the males attained 
GM5 
lampsilis' 
~r 
rTTTTin riii 
WEIGHT . AGE . AND SEX 
wr 
TO 
\N0D0NT0IDES 
ON LENGTH 
A 
? 
7 
MISSISSIPPI RIVER, 1A. 
t 
t 
d 1 
iff 
m 
fa: 
% 
'fa 
i 
1 
£_J 
§ 
CMS 8.0 8.5 9.0 S.5 10.0 10.5 1 1.0 11.5 12.0 12.5 
Figure 13. — Bar graph showing weight, sex, and age plotted against length, for 
yellow sand shell at Fairport, Iowa 
this size in 3 years, while the females required 4 because of their greater thinness of 
shell. Figure 13 shows the weight values with sex for the various year classes of the 
Mississippi specimens of the species for which weight values were taken, imposed on 
length. Actual values are given in Table 8. 
THICKNESS IN RELATION TO AGE 
The thickness of the shells of the various year classes from each locality was 
measured. For the sake of uniformity, this measurement was taken at a correspond- 
ing point on each specimen ; namely, immediately dorsal to the pallial line on a line 
at right angles to the long axis of the shell, passing from the umbo across the shell. 
Thickness was measured with a pair of steel bow calipers with screw adjustment. 
Table 8. — Weight, age, and sex in relation to length of yellow sand shell, Lampsilis anodontoides {Lea), 
in Mississippi River, Iowa 
Ring 
Length 
Weight 
Sex 
Ring 
Length 
Weight 
Sex 
III 
Centi- 
meters 
8. 22 
Grams 
15.3 
Male. 
VI 
Centi- 
meters 
11.50 
Grams 
5G. 0 
Female. 
IV 
9. 57 
29.7 
Do. 
VII 
11.90 
71.5 
Male. 
V 
10.38 
42.5 
Do. 
VII 
11.90 
64.6 
Female. 
V 
10.83 
46.9 
Female. 
VIII 
12. 30 
77.9 
Do. 
\i 
11.30 
54.0 
Male. 
