Neritidae科腹足類における蓋の内部構造と鉱物

概要

論文の詳細を見る
The internal structure and mineralogy of the calcined opercula of eight species of neritid gastropods have been studied. The neritid opercula studied consist of an organic layer and two or three calcined ones. They are classified into two types, "separate" and "non-separate", from a developing manner of the organic and calcified layers. In the separate type, the calcification is performed on both the inner and outer sides of the organic layer so that the calcified opercula appear to be separated into two parts by the organic layer. In the non-separate type, the inner and outer calcified layers directly contact with each other, and a reduced organic layer attaches only to the periphery of the outer calcified layer along the outer-lip-side margin. The latter type may be derived from the former in the course of the evolution of the gastropod operculum. Every calcified layer is aragonitic with a small amount of organic matrices. The micro-structure is identified with the irregular prismatic structure. This microstructure tends to change gradually into a type of the complex crossed-lamellar structure, which is characterized by the irregular arrangement of the crystal aggregations within which acicular crystals are well ordered. This orderliness of crystal arrangement is probably due not to a geometric selection but to the other mechanism such as a split growth of crystal.
地学団体研究会の論文
1988-05-25