Abstract
Fossil specimens of Saxidomus purpurata（Bivalvia:Veneridae） collected from Holocene marine deposits at Yokosuka and Tateyama, Central Japan were analyzed to investigate shell breakage and effectiveness of boring. They were divided into four test groups by locality and habitat. A valve was partitioned into five sections; anterior, dorsal, center, ventral and posterior section. The positions and the number of shell breakages are counted and the frequencies of breakages are compared among 1) five shell sections, and 2) four test groups. As the result of the observation, it is suggested that most of the shell breakages significantly occurred in ventral and posterior sections. In contrast, no significant difference is determined among the test groups. It is concluded that boring into base rock is little effective against physical agents and/or predations if the clam bores not more than its shell length.
