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xiii, 141 p. : ill. (some col.) / The small trochid gastropod <italic>Lirularia succincta</italic> occurs in rocky intertidal habitats along the Pacific coast of North America. Strong escape responses of adult <italic>L. succincta</italic> were elicited by the predatory seastars <italic>Leptasterias hexactis</italic> and <italic>Pycnopodia helianthoides</italic> but not by the nonpredatory seastar <italic>Henricia</italic> sp. Escape responses to juvenile <italic>L. hexactis</italic> were not observed in newly-hatched <italic>L. succincta</italic>. The snails exhibited weak avoidance responses to water-borne chemical stimuli from <italic>L. hexactis</italic>. The vertical distribution of a population of <italic>L. succincta</italic> was described, and changes in the size-frequency distribution of the population in the spring and summer were documented. Finally, factors that may affect oviposition in <italic>L. succincta</italic> were investigated in the laboratory. The snails deposit egg masses year round with a peak in reproductive output in the summer. In the laboratory and in the field, egg masses are preferentially deposited in crevices. / Committee in charge: Dr. Craig M. Young, Chair; Dr. Richard B. Emlet, Member; Dr. Alan L. Shanks, Member