S. Poivers — Gastropod Trails in Sandstones. 107 



trails. The ridges in the modern trails point forward 

 and may be present or absent according to the firmness of 

 the sand. Professor Raymond finds that both the direc- 

 tion and the preservation of the modern trails is depend- 

 ent npon the condition of moistnre on the beach as well as 

 upon the composition of the beach surface. The gastro- 

 pods make the trails when the beach is out of water and 

 early drying is necessary for preservation. In addition 

 to the positive evidence of the gastropodous origin Pro- 

 fessor Raymond notes that the eccentric winding course 

 is very different from the straight trails made by 

 annelids. It is therefore concluded that both types of 

 the Shafter trails were made by gastropods and that the 

 difference between these trails was dependent upon physi- 

 cal conditions rather than upon different species of 

 gastropods. 



