lxxxiv PROCEEDINGS OE THE GEOLOGICAL SOCIETY. [vol. lxxix, 



millions of a blue-green alga — Triclioclesmhim. It is in the 

 highest degree probable that similar algae were among the earlier 

 inhabitants of the Palaeozoic oceans. 



Several authors have expressed the opinion that the Blue-Green 

 Algae existed in early Palaeozoic times. The attributes of present 

 members of the group encourage the expectation of discovering 

 fossil representatives among the oldest geological records, and such 

 evidence as Dr. Walcott has furnished, although admittedly not 

 conclusive, lends support to inferences based solely on the 

 characters of living plants. Definite evidence has been supplied 

 by Prof. M. D. Zalessky, who found in an Ordovician deposit in 

 Central Esthonia known as Kuckersite (from the locality Kuckers) 

 numerous small aggregates of minute cells with mucilaginous 

 walls, which he compared with colonies of the recent blue-green 

 alga Gloeocapsa, and named Gloeocapsa prisca. I am indebted to 

 Mr. John Walton for preparations of these bodies, from a sample 

 of Kuckersite generously sent to me by Prof. Zalessky. A Swiss 

 investigator, Dr. H. A. E. Lindenbein, prefers to regard the 

 Ordovician species as a member of a family for which he suggests 

 the designation Protophycese, characterized by a combination 

 of certain features now shared by the Blue-G-reen and Red Algae. 

 The material which I have examined leads me to think that there 

 is no adequate reason for doubting the correctness of Zalessky's 

 conclusion. 



Beneath the waters of some recent lakes there is accumulating 

 a slimy material formed of the partly decomposed remains of 

 small animals and plants of the plankton population. To this 

 material, which contains many spores protected by their resistant 

 membranes, Dr. H. Potonie gave the name sapropel. Certain 

 carbonaceous beds such as boghead, torbanite, and others occurring 

 at various geological horizons are believed to be fossil sapropels : 

 these contain flattened sac-like bodies described by authors as Pila 

 and JRheins cliia, and referred to the Algae, but by Prof. E. C. 

 Jeffrey identified as spores of Vascular Cryptogams. Although 

 there is a superficial resemblance between the Kuckersite organisms 

 and Pila and Hheinscliia, the former are clearly not sacs like the 

 bodies included in the last-named genera, but irregularly branched 

 cell-aggregates : if not Blue-Green Algae, they are, I believe, at 

 least closely allied plants, which lived in stagnant lacustrine 

 water during the Ordovician Period. 



