550 
BULLETIN OP THE BUREAU OF FISHERIES 
Table 4. — Median lengths of males and females from Hallo Bay to correspond with Figure 4 
Ring 
number 
Males 
Females 
Ring 
number 
Males 
Females 
Ring 
number 
Males 
Females 
Length 
Num- 
ber of 
speci- 
mens 
Length 
Num- 
ber of 
speci- 
mens 
Length 
Num- 
ber of 
speci- 
mens 
Length 
Num- 
ber of 
speci- 
mens 
Length 
Num- 
ber of 
speci- 
mens 
Length 
Num- 
ber of 
speci- 
mens 
Cm. 
Cm. 
Cm. 
Cm. 
Cm. 
Cm. 
1 
0. 39 
37 
0. 32 
51 
8 
13. 56 
97 
13. 76 
95 
15. 
15. 85 
15 
15. 67 
12 
2... 
2. 07 
111 
2. 48 
115 
9__ 
14. 05 
93 
14. 07 
89 
16 
15. 62 
8 
15. 50 
2 
3 
5.05 
113 
6. 22 
116 
10 
14. 44 
88 
14. 46 
84 
17_ 
15. 74 
4 
4 
8. 01 
113 
9.21 
116 
11 
14. 77 
73 
14. 77 
65 
18.. 
16. 31 
3 
5 
10. 59 
112 
11. 33 
116 
12.. 
15. 13 
57 
14. 98 
54 
19 
16. 74 
2 
6 
12. 21 
111 
12. 59 
116 
13 
15. 42 
42 
15. 28 
35 
7 
13. 10 
105 
13. 27 
100 
14 
15.60 
28 
15.42 
24 
Whether the greater difference in the size of the males and females in this series 
is peculiar to the locality or whether the method of taking the shells did not give an 
accurate sample, it is impossible to determine. The shells were taken from two lots of 
0 2 4 <5 <3 IO 12 H 16 IQ / 9 
Age (Vears) 
Figure 4. — Growth curves for males and females taken in Hallo Bay, Alaska. Age is indicated 
as ring number; to determine actual age subtract one-half year 
clams which may have come from different localities. One sample contained over 
one-half males and the other a larger number of females, so the significance is doubtful. 
However, these results are similar to those of Copalis, Wash., although the differences 
are more marked. The curves in the latter case cross and recross in a similar manner 
at corresponding periods in their life cycle. Differences in the growth curves of the 
sexes in mollusks have been described by Chamberlain, who found the course of 
growth to vary between sexes of fresh-water mussels 2 (1931). In this case, however, 
the sex is indicated by the shape of the shells, and one can easily determine the sex 
of the animal from its appearance, while in razor clams weights and proportional 
measurements of the shell do not show sexual differences. Since the number of each 
sex is approximately equal, it is assumed that a composite curve calculated from growth 
records of both sexes, if taken in a limited habitat, is adequate for growth study. 
MORTALITY 
One striking feature in the study of clams from all parts of the coast is the differ- 
ence in age found between northern and southern beds. No clams over 5 years old 
1 Thesis, Stanford University. 
