322 
MR. W. BATESON ON SOME VARIATIONS OF CARDIUM EDULE 
The Fourth Terrace. 
(a.) Shells Varying in Length between 21 mm. and 16 mm. 
Measuremente of shells in millimetres. 
Average breadth of shells having the same length. 
Eatio of length to 
breadth. 
j 
Length. 
Breadth. 
Length. 
Average 
breadth. 
Number of 
shells. 
21 
16-5, 16, 15-5, 15(2) 
21 
15-4 
5 
i 1:0-73 
20-5 
16-5, 16. 15(2) 
20-5 
15-6 
4 
1 -76 
20 
16, 15, 14-5, 14(3) 
20 
14-5 
6 
1 -7-2 
19-5 
15, 14(2) 
19-5 
14-3 
3 
1 -73 
19 
14, 13-5, 13 
19 
13-5 
3 
1 ‘71 
18-5 
13 
18-5 
13 
1 
! -70 
18 
14. 13 
18 
13-5 
2 
1 -74 
17-5 
14, 13 
17-5 
13-5 
2 
' -77 
17 
13 
17 
13 
1 
•76 
16 
12-5, 12, 11-5 
16 
12 
3 
•75 
Average ratio of length to breadth in 30 shells varying in length between 16 mm. and 21 mm. 
is 1; 0-73.5. 
(b.) Shells Varying in Length between 26 mm. and 18 mm. 
1 
Measurements of shells in millimetres. ^ 
Average breadth of shells having the same length. 
Eatio of length to 
breadth. 
Leng-th. 
Breadth. | 
Lengih. 
Average 
breadth. 
Number of 
shells. 
26 
19 
26 
19 
1 
1 : 0-73 
25 
18 
25 
18 
1 
•71 
23 
18, 17-5, 16 
23 
17-1 
3 
•74 
22-5 
17 
22-5 
17 
1 
•75 
21 
16-5, 16, 15-5, 15(2) 
21 
15-4 
5 
•73 
20-5 
16-5, 16, 15(2) 
20-5 
15 6 
4 
•76 
20 
16, 15, 14-5, 14(3) 
20 
14-5 
6 
•72 
19-5 
15, 14(2) 
19-5 
14-3 
3 
•73 
19 
14, 13-5, 13 
19 
13-5 
3 
•71 
18-5 
13 
18-5 
13 
1 
•70 
18 
14, 13 
18 
13-5 
2 
•74 
Average i-atio of length to breadth in 30 shells varying in length between 26 mm. and 18 min. 
is 1 : 0-730. 
