lxxvi PROCEEDINGS OF THE GEOLOGICAL SOCIETY, [vol. lxxix, 



that there are no adequate grounds for regarding such structures 

 as those designated Cryptozoon and AtiTcohania, or the comparable 

 forms from Carboniferous rocks described by G. GKirich, as fossil 

 algse or as^he products of algal life. There remains the possibility 

 that a clue to the interpretation of such structures may be found 

 in the class of phenomena represented by the so-called Liesegang 

 fig vires, to which further reference is made later. 



In a contribution entitled ' Pre- Cambrian Algonkian Algal 

 Flora ', Dr. C. D. Walcott described several new genera from the 

 Cordilleran region of North America, founded on rock-structure 

 which he believes to have been formed through the agenc^y of algse 

 closely allied to the Cyanophycese. These so-called algse occur 

 in the Newland Limestone of the Belt Series of Montana, possibly 

 in part at least of Pre- Cambrian age, from the base to the summit 

 of a succession of beds 2000 feet thick. It is impossible in the 

 time at my disposal to give a description of the various calcareous 

 bodies described by Walcott : the characters on which the supposed 

 generic distinctions are based are shown in the published plates. 

 My own first-hand acquaintance with them is limited to an exami- 

 nation of some specimens presented by Dr. Walcott to the British 

 Museum. It is with considerable reluctance that I presume to 

 criticize the conclusions of so distinguished a geologist as 

 Dr. Walcott, but it would be less than honest to refrain from ex- 

 pressing my opinion, however little value it may have. All agree, 

 •as Walcott states, 



"' in not having the structure of the higher Algse. All appear to have been 

 deposited in successive layers, the inner and older serving as a foundation in 

 which the younger filaments grew in variously arranged forms.' 



That their formation Avas in any way connected with algse is hypo- 

 thetical. The only evidence of the association of any of these 

 bodies with algse is that, in a very few examples, the residue" left 

 after treatment with acid revealed the presence of a small number 

 of exceedingly minute cell-like structures. If these be cells, their 

 presence does not prove any organic origin for the associated cal- 

 careous masses. My attention was drawn by Mr. W. N. Edwards, 

 of the Geological Department of the British Museum, to the 

 resemblance of some of Walcott's genera to concretions found in 

 the Magnesian Limestone from the Durham coast. Careful exami- 

 nation of these concretions led me to suspect very strongly that 

 if, as is generally believed, they are of inorganic origin, a similar 



