Gross Anatomy of Campeloma. 495, 
TABLE OF DIMENSIONS. FEMALES. 
| 
No i; II No. | I, H. No. Fi ii, 
mm. mm. | mm. mm. mm. mm. 
1 36.44 18.40 18 | -85.50 17.72 25 29.20 16.22 
2 30.00 15.68 14 30.80 16.29 26 29.10 15.80 
3 29.80 5.16 15 82.37 6.40 27 32.88 16.34 
4 32.12 6.00 16 30.50 5.56 28 30.24 16.60 
5 32.92 16.88 17 28.50 5.68 23.94 12.86 
6 30.26 16.21 18 33.14 6.80 30 25.84 12.92 
7 30.44 15.50 19 29.49 32 31 26.16 29 
8 33.62 8.62 20 80.00 15.50 82 95.16 12.92 
9 35.28 | 17.62 21 31.64 17.36 33 25.50 13.60 
10 29.88 5.72 22 83.14 16.16 34 23.86 12.24 
11 83.50 16.60 23 85.4 17.32 24.95 12.88 
12 32.50 7.00 24 30.42 16.56 36 24.00 | 12.64 
I. = length in mm. II. = diameter in mm. 
A comparison of ratios shows the numerical values of differ- 
ences, as follows: Length of male to its diameter, 23 $$$; length 
of female to its diameter, 34 37; length of female to length of 
male, 3133.; diameter of female to diameter of male, 18 434. 
The differences of lengths is 5.561 and of diameters 2.893. It 
would appear, then, that this degree of difference may be of diag- 
nostic value in the matter of sex. The diagram, Fig. 3, is designed. 
to present this sexual peculiarity in a graph- = 
ic form. The marginal numbers represent 
millimetres. The ordinates represent the 
lengths, and the ubscissas, which have the w -~ 
Same scale, represent diameters. The cir- 
cular conventional sign represents the male 
and the triangular character the female spec- 
imen. The average dimensions of each `~.. 
group are represented by the open conven- 
tional sign with its distinguishing sex mark 
conjoined. It will be seen that while the 
dots fall into two pretty well-defined groups, 
the range of greatest variation follows the ordinates, and that this 
range is comparatively greater for the female than for the male form. 
In other words, the males are more constant in lengths and vary less 
in diameter, while, for the female form, differences in length are 
measurably compensated by corresponding increase in diameter. 
In connection with this character it may not be altogether amiss. 
to call attention to certain so-called species which have been based — 
upon the males of C. subsolidum. They are Campeloma milesii Lea, 
wa > aaa ay 
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771 
Tig 3 
