ABSTRACT

Statistical treatment of collections of valves of the clam Dinocardium robustum deposited on the beach of Mustang Island, Texas, indicates the differences in the number of left and right valves are significant at the 0.05 level of probability. A relationship is shown to exist between average valve length and the percentage of excess valves, with the number of excess valves being significant only in collections having an average valve length greater than 69.5 mm. This relationship is attributed to a similarity in surf requirements for separating opposing valves and transporting large valves, namely a high energy surf. Differences in weight, ornamentation, and fragility between opposing valves do not affect their distribution. Boring snails attack left and right valves in equal n mbers, but seem to prefer small sizes. The size-frequency distribution of collections are varied, but highly skewed curves predominate.