494 Gross Anatomy of Campeloma. 
The number of young is variable, the large mature specimens 
containing, as might be expected, the greater number of young 
shells. ‘Twenty specimens were carefully examined with a view to 
this feature, with the following result :— 
= Young. popan Young. | Sip | Young. bo Sings Young. 
| | 
1 36 6 wn n 2 16 47 
2 42 7 62 |] 12 | 17 42 
8 51 8 2 Pe he 18 64 
4 35 9 s or u 58 19 63 
5 41 10 38 || 16 34 20 50 
| pa 
These twenty individuals, therefore, present an average of forty- 
three young. 
Aside from the tentacular differences which exist between the 
male and female, both tentacles of the latter being uniformly sub- 
ulate, a further sexual difference appears in the greater size and 
somewhat more globose character of the female shell. Coördinated 
with this difference in dimensions is the more shouldered character of 
the whorls in the female specimen, a difference connected with the 
position and necessarily large size of the gestatory sac. The males 
are more regularly conical, with rather less oblique aperture, and 
are of considerably less globose appearance than are the females. 
This difference was supposed to be of value in determining the sex 
when only the shell was at hand. To test it as a sexual differen- 
tial character, thirty-six of the largest males and an equal number 
of the largest females were selected from a finding of more than a 
gallon of C. subsolidum, taken on August 6, 1887, and were care- 
fully measured. The results appear in the following :— 
TABLE OF DIMENSIONS. MALES. : 
} 
No. 1 | II No I. fi. No I II 
mm. | mm. mm. mm. 
1 25.88 | 12.80 13 24.94 | 12.92 | 25 24.22 | 12.36 
2 | 28.00 | 13.00 | 14 | 24.52 | 1238 | 26 | 25.14 | 13.00 
3 27:25 |: 18.82 9°15 26.10 | 13.51 f 27 23.90 | 12.70 
4 26.06 | 13.31 16 80.76 | 15.00 26.62 eo 
5 27.22 | 12.90 17 27.34 14.00 f 29 23.94 2.86 
6 26.80 | 13.14 18 24.95 | 18.86 f 30 25.84 | 12.92 
7 27.47 | 15.08 19 27.82 | 18.04 f 31 26.16 bg 
8 25.50 | 12 20 26.86 | 14.20 E 32 25.16 Be 
9 24.48 | 12.54 21 25.76 | 13.62 25.50 | 13. 
10 A e 22 25.20 | 18.61 § 34 23.36 oT 
11 26.28 | 13.40 23 24.82 | 13.50 f 35 24.95 ret 
12 24.14 | 12.50 24 28.82 | 15.22 f 36 24.00 
I. = length in mm, II. = diameter in mm. 
