Abstract: The 2nd member of Shahejie formation is an important oil bearing series of the area with abundant Gastropoda fossils which provide an effective means to reconstruct the paleogeographic landscape of their habitat. Characteristics and distribution of their assemblage are reviewed, with particular emphasis on the occurrence, evolution and environment of the predominant genus Tulotomoides. The changes of surface relief of the 2nd member of Shahejie formation as shown in the section indicate the contraction of the lake basin from east toward the west, which caused the eventual disappearance of the Dongying Lake with the encroachment of the alluvial plain.

摘要： 沙河街组二段是本区的重要含油层系。其中腹足类化石丰富。用其生活环境恢复当时的古地理景观较为有效。文中主要叙述了沙河街组二段腹足类的组合特征及其分布,着重描述了优势属——Tulotomoides的发生、发展和生活环境,在剖面上阐明了沙河街组二段的古地理变迁。主要表现为湖盆由东向西退缩,致使这一时期的东营湖最终被冲积平原的侵占而消失。