APPARENTLY CORRELATED TO THE CONDITIONS OF LIFE. 
323 
The Fifth Terrace. 
[a.) Shells Varying in Length between 21 mm. and 16 mm. 
Measurements of shells in millimetres. 
Average breadth of shells having 
the same length. 
Eatio of length to 
breadth. 
Length. 
Breadth. 
Length. 
Average 
breadth. 
Number of 
Shells. 
21 
17, 16-5, 16(2), 15-5 
21 
16-2 
5 
1 : 077 
20-5 
15 
20-5 
15 
1 
73 
20 
15-5, 14 
20 
147 
2 
73 
19-5 
14-5, 14 
19-5 
14-2 
2 
73 
19. 
15,14(h, 13-5, 13 
19 
13-9 
7 
73 
18 
14(2), 13-5 
18 
13-8 
3 
73 
17-5 
13-5, 13 
17-5 
13-2 
o 
75 
17 
13-5, 13(2), 12-5 
17 
13 
4 
76 
16 
13, 12-5, 12(2) 
16 
12-3 
4 
77 
Average ratio of lengtli to breadth in 30 shells varying in length between 21 mm. and 16 mm. 
is 1: 0743. 
[h.) Shells Varying in Length between 27'5 mm. and 21 mm. 
Measurements of shells in millimetres. 
Average breadth of shells having 
the same length. 
Eatio of length to 
breadth. 
Length. 
Breadth. 
Length. 
Average 
breadth. 
Number of 
shells. 
27-5 
19 
27-5 
19-5 
1 
1 : 0-70 
26 
20, 19, 18 
26 
19 
3 
-73 
25-5 
17 
25-5 
17 
1 
-67 
25 
19-5,19, 18-5, 18, 17-5 
25 
18-5 
5 
-74 
24 
19(2), 18-5, 18, 17-5 
24 
18-4 
5 
-75 
23 
17, 16-5(2), 16(2) 
23 
16-4 
5 
-71 
22-5 
17(2), 15-5 
22-5 
16-5 
3 
-73 
22 
17-5, 17, 16-5,15 
22 
16-5 
4 
-75 
21-5 
16 
21-5 
16 
1 
"74 
21 
17, 16 
21 
16-5 
2 
-73 
Average ratio of length to breadth in 30 shells varying in length between 27‘5 mm. and 21 mm. 
is 1: 0731. 
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