Date of Award

Summer 1970

Document Type


Degree Name

Master of Science (MS)


Ocean & Earth Sciences



Committee Director

John C. Ludwick

Committee Member

Jacques S. Zaneveld

Committee Member

Gerald L. Shideler

Committee Member

M. Keith Garrett

Call Number for Print

Special Collections LD4331.O35 B63


Erasure of sediment surface features by individuals of the species, Mellita guinguiesperforata, observed in this study suggests that all members of the sub-order, Scutellina, are able to erase sediment surface features. Sweep time, the time needed to erase the surface features of an area, depends on the population density, individual size, and speed of movement of the sand dollars. Assuming their pattern of movement as random, the following equation can be used to determine sand dollar sweep time,

T - 3.2 N-0.76 (W / S) (A/ W2 )1.21

where T is sweep time, N is the number of sand dollars, W is the average sand dollar width, S is their average speed, and A is the area under consideration. Known since the Eocene epoch, individuals of Scutellina may have erased sediment surface features in the past, thus giving reason for some sandstones being devoid of such features.


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