In his article on septarian structure in the March number of the GEOLOGICAL MAGAZINE Dr. A. Morley Davies seems to call for further light upon the subject, hence the following is offered. The writer became convinced of the fallacy of the current teaching concerning the formation of concretions with cracked interiors and of septaria more than thirty years ago, and has so taught in his classes ever since. In 1902 he published a paper on “Concretions and their Geological Effects”, which presented facts which virtually demonstrate that the cracking is due to the expansion of the exterior rather than by a contraction of the interior, as Dr. Davies has also concluded.