Article: The median abdominal appendage of the Silurian eurypterid Slimonia acuminata (Salter)

The results of a study of a series of specimens exhibiting the median abdominal appendage of Slimonia acuminata (Salter) from the Upper Silurian of Logan Water, Lesmahagow, Lanarkshire, are given. The anatomy of the opercular appendage of both sexes is redescribed in the light of knowledge obtained from recent work on related structures in other eurypterids, and the segmented nature of the appendages demonstrated. Stages in the development of the appendage in both sexes in ontogeny are described for the first time.