. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 0,0 - CD a a. o 00 - 20 40 60 80 SHELL HEIGHT (mm) 100 I 120 Figure 5. Position of external lines and shell carbonate oxygen isotopic record for specimen PM26. The external lines illustrated in the diagram are those which were interpreted by NMFS personnel as representing years of growth. As in Figure 4 for specimen PM10, the Hnes are numbered in reverse chronological order, and the oxygen isotopic values for shell carbonate samples are plotted with a reversed d'^O scale. begins at 30 mm, reaches a late summer tempe
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 0,0 - CD a a. o 00 - 20 40 60 80 SHELL HEIGHT (mm) 100 I 120 Figure 5. Position of external lines and shell carbonate oxygen isotopic record for specimen PM26. The external lines illustrated in the diagram are those which were interpreted by NMFS personnel as representing years of growth. As in Figure 4 for specimen PM10, the Hnes are numbered in reverse chronological order, and the oxygen isotopic values for shell carbonate samples are plotted with a reversed d'^O scale. begins at 30 mm, reaches a late summer temperature maximum at approximately 55 mm, and proceeds to a yearly minimum at 65 mm shell height. The beginning of a third annual cycle represented by the last 10 mm of shell and terminating at the ventral margin coincides well with the spring collection date (Fig. 4). Not only does the beginning of the isotopic cycle coincide with the seasonal hydrographic cycle, but the 6'^0 values of samples taken from the shell margin are very close to the \J%o value predicted by the model for May (Fig. 3). This agreement between isotopic "season" and collection date supports the validity of the isotopic record interpretation. These results indicate a discrepancy between the three years of growth interpreted from the external lines and the two years of growth inferred from the 6"*0 record. Further, the external lines, which are presumed to be deposited annually in the spring, appear to occur in various seasons according to the inferred seasonality of the isotopic profile. For example, external line number 3 was deposited in the fall of the first growth year, line 2 during summer of the second year, and line 1 the following spring (Fig. 4). In this particular specimen, there does not appear to be a consistent season. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illus
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