A YORKSHIRE NATURALIST 183 



special attention to these anomalous organisms, 

 and my results were embodied in a memoir, "On 

 " some Undescribed Tracks of Invertebrate Animals 

 " from the Yoredale Rocks, and on some Inorganic 

 " Phenomena Produced on Tidal Shores, Simulating 

 " Plant Remains." This memoir was published in the 

 tenth volume of the third series of " Memoirs of the 

 " Manchester Literary and Philosophical Society," 

 session 1884-1885. 



During a holiday at Llanfairfechan, in North 

 Wales, two years prior to the above date, my 

 attention was arrested by the small drainage streams 

 that followed the retiring tide. I cannot better 

 explain the nature of these conditions than by 

 quoting a brief passage or two from my memoir. 

 " These contours, produced by many of the smaller 

 "tributaries, where they united to form larger 

 " streamlets, suggested to my mind the extreme 

 " probability that the casts of such sculptured areas 

 " would, if found in any of the older strata, be un- 

 " distinguishable from many of the so-called fossil 

 " Fucoids found in these strata." I succeeded in 

 obtaining a number of plaster casts of the more 

 striking of these conditions, and presented them to 

 Owens College Museum, where they are now pre- 

 served, and photographs of some of these casts 

 illustrate my memoir. Had such specimens been 

 found on the inferior surfaces of ancient flag- 

 stones, I have little doubt but that they would have 

 appeared in the pages of Schimper and other authors 



