Predicted area was determined by using the least square correlation line between measured area and length squared for complete good and excellent specimens. Since these specimens had lost no area they were used to estimate the relationship between area and length for unfragmented valves.
| Lower Zone | Upper Zone | Complete | 80.2% | 57.5% | Fragmentary | 19.8% | 42.5% |
Chione cancellata valves from the Upper Zone were more likely to be fragmented than those from the Lower Zone. Because of the greater percentage of fragmented valves, the average area loss for the Upper Zone is greater than from the Lower Zone.
Curiously, while fragmentation was more common in the Upper Zone, the amount of fragmentation of individual valves did not vary by zone.
In each zone, average fragmentation of individual valves was approximately 75%.
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