"The material for this work came from an extensive temporary exposure in the Vale of Belvoir (south Notts) which cut across the outcrops of some 70 feet of lower Liassic beds. Approximately one-third of the Gryphaea shells carried developmental stages. The youngest of these consisted of larval shells closely resembling those of the modern Ostrea. During the breeding season larvae settled at least twice. The growth of spat is described. The great majority of these died in early life and relatively few grew to later stages. About 5 per cent broke loose. Many of the host shells started life attached to small shells or fragments. A study of life conditions throws light on the course of deposition in Liassic waters."