38 



exhibited and described. One of these series represented 

 branching forms easily mistaken for Fucoidal remains. They 

 were in reality casts, made in plaster of Paris, of remarkable 

 drainage lines left by the retiring tide, on the sandbanks at 

 Llanfairfechan, in N. Wales. 



The second series consisted of allied objects, but in this 

 case drainage lines had combined with ripple marks to pro- 

 duce an effect easily mistaken for the geometrically arranged 

 scale-leaves of some Cycadean stem. These casts were 

 obtained from sandbanks to, the north of Barmouth. 



The author called attention to the controversy bearing on 

 these subjects still in progress, especially between Professor 

 Nathorst and the Marquis of Saporta, and renewed an 

 objection, recorded in more than one of his previous publica- 

 tions, to such anomalous objects as those in dispute being 

 made use of, when attempting to frame, from Palceontological 

 evidences, a pedigree of the vegetable world. 



It was moved by the President, seconded by Dr. Bottomley, 

 and resolved unanimously, That the thanks of the Society 

 be given to Mr. Brothers for having presented to the Society 

 photographic illustrations of the specimens discussed in the 

 President's Memoir. 



Ordinary Meeting, February 24th, 188.5. 



Professor W. C. Williamson, LL.D., F.RS., President, 

 in the Chair. 



"On Unipolar Convolutes," by the Rev. H. London, M.A, 



Let a string of fixed length be wrapped round a curve, 



and let the free end be fastened to a given point. If then 



the string be kept stretched by a pencil point dividing it 



into two segments, and if the string be unwrapped from the 



