362 



J. E. Todd — On Septarian structure. 



Figs. la-e. A series of drawings illustrating the growth of a concretion 



having cracked interior, caused by the expansion of the exterior by 



more rapid interstitial deposition in that portion. 

 Fig. 2. Diagram of a compound calcareous concretion from the Loess of 



Eastern Nebraska. The different members were doubtless added in 



the order indicated {a-d). 

 Figs. So-c. Photographs of fragment of such a concretion. 



