In the first part of this work, minerals elaborated by molluscs was discussed on the phylogenic viewpoint. Secondly, the crystal formation of shell minerals in molluscs was considered in the following two cases ; (1) initial calcification, and (2) additional calcification. The crystal formation in the initial calcification in glass coverslip preparations of Pinctada fucata and Pinna attenuata was investigated by electron microprobe analyzer, and scanning electron microscope with energy dispersive type X-ray spectrometer, and compared with that in additional calcification during the growth of nacre of bivalve molluscs.
