Institute of Geosciences, Shizuoka University, 836 Oya, Shizuoka 422-8529, Japan
(Received March 5, 2001; Accepted May 21, 2001)
Keywords: Prisms, Bivalve Shells, Theoretical Morphology, Biomineralization
Abstract. The sizes, morphologies and distribution of nucleation sites of aggregated prisms on the outer shell surface were examined in 38 species of the Bivalvia and modeled theoretically. Biometric analysis reveals the following: 1) the cellular pattern of prismatic structure tends to close with Voronoi divisions with increasing the size of prisms, and 2) nucleation of prisms tends to occur at regular intervals in the case of the low density of nucleation. Comparison of the results of biometric analysis with those of computer simulations show that the period of nucleation stage in which prisms can be born primarily controls the shapes and distribution of nucleation sites of aggregated prisms. The result of this study suggests that the crowding of nucleation is regulated so as to keep a distance between prisms.