Measurements of individual shell size can help with species identification, but more importantly, can allow us to build demographic profiles of a species that show whether human collecting has produced any kind of size bias in the sample of discarded shells. This profile of Rabdotus sp. shell height comes from the entire sample column at the Vara Daniel site in Austin. It shows a bimodal distribution with significant juvenile mortality, and no marked preference for adults. This looks like a natural population profile, and it can be compared to size profiles from the contemporary San Marcos samples.

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