304 IPostelsia 



Plate XXI. I. Small depressions in sand- 

 stone near high water line. 



2. Regions of young pools. 



Plate XXII. I. and 2. Irregularities in outer 

 shore line arising from wearing out of tide- 

 pools. 



Plate XXIII. I. Irregular pools formed by 

 union of several small pools. 



2. Series of pools reaching above 

 ordinary high water. 



Plate XXIV. Tide rift formed from several 

 pools. 



Plate XXV. I. Tide-pools in various stages 

 of development. 



2. Tide-pools formed in shale. 



