SIZE DISTRIBUTION, EROSIVE ACTIVITIES, AND GROSS METABOLIC EFFICIENCY OF THE MARINE INTERTIDAL SNAILS, LITTORINA PLANAXIS AND L. SCUTULATA ,

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Abstract
1. Size distribution curves for populations of the marine intertidal snails Littorina planaxis and L. scutulata in three environments are presented. 2. It is concluded that environmental factors cause the observed size distributions, and the amount of wave action at a given locale appears to be one of the influencing factors. L. planaxis was observed to cling to a smooth surface in current velocities of two to three meters per second for 10 seconds. 3. The time for littorines to cycle food completely through the gut varied with size. Snails 0.8 cm. in height required from 2½ to 6 hours. 4. Erosion resulting from the snails' feeding activities was estimated for certain tidepools and found to deepen tidepools one cm. every 16 years. This is of the same order of magnitude as other erosive processes which have been studied in the same region. 5. Growth of L. planaxis was found to average 0.02 cm. per month in height increment, and 0.6 mg. per month in dry weight of organic matter. 6. The gross metabolic efficiency was computed and is estimated to be in the neighborhood of 7%.