452 Annals New York Academy of Sciences 



and visibly devoid of internal structures or inclusions. Whether these repre- 

 sent coenocytic algae or fungi is not possible to determine, although the general 

 form and undulating outline of the filaments is more characteristic of algae than 

 of aquatic fungi. Among the larger nonseptate filaments very occasionally 

 forms have been observed in which the lumen of the filament contains numerous 

 spherical sporelike bodies. In living organisms a somewhat comparable 

 morphology may be found among certain of the iron bacteria {Crenothrix poly- 

 spora). 



The sporelike bodies which are ubiquitous and irregularly distributed 

 throughout thin sections of the chert vary in size between 1.0 to 16.0 /x in 

 diameter (measured along the long axis if ellipsoidal). They are predom- 

 inantly spheroidal and are not appendaged. The range in size, thickness 

 of wall, and variation in the sculpture pattern of the wall residues indicates that 

 they comprise an assemblage of forms the morphology of which gives little clue 

 to phylogenetic aflinity. 



A very common and distinct organism in certain facies of the Guntiint chert 

 is an entity whose closest morphological comparison among living organisms 

 can be found in certain groups of the phylum Coelenterata. Rather than to 

 accept the existence of coelenterate animals in an assemblage of such geological 

 age as the Gunflint sediments exhaustive efforts have been made to compare 

 these structures with algae, various of the larger colonial bacteria, and protozoa. 

 It has not been possible, however, to find morphologically comparable struc- 

 tures in these diverse groups and the authors have been forced to conclude, on 

 the grounds of morphology, that the organisms most probably represent meta- 

 zoons, the closest structural affinity of which is among the Coelenterata. A de- 

 tailed description of these organisms and other microstructures occurring; in the 

 chert will be made in a forthcoming paper dealing with the detailed geology and 

 paleontology of the (iunflint chert. 



The organic fraction of the darker and more organic samples of the Gunflint 

 chert varies between 0.2 to 0.6 per cent by dry weight. As previously noted 

 Si02 comprises the major mineral component and constitutes more than 99 per 

 cent of the dry weight of much of those chert samples that exhibit the best 

 preservation of organic structures. The organic residues yield small amounts 

 of benzol-acetone-methanol soluble substances, probably hydrocarbons of 

 molecular weights C20 or above. These extracts fluoresce strongly in ultra- 

 violet light. Upon destructive distillation at 400° C. the insoluble organic resi- 

 dues yield small amounts of aliphatic hydrocarbons, chiefly methane (87 ppm), 

 ethane (4 ppm), and propane (0.7 ppm) and traces of aromatic hydrocarbons 

 (benzene, 0.34 ppm; toluene, 0.15 ppm; xylenes, 0.45 ppm). Degassification 

 of the chert at room temperature yields methane (6.0 ppm) and butane (0.2 

 ppm). The chemical data, although limited, are entirely consistent with the 

 paleontological interpretation that the black chert represents the silicified re- 

 mains of a biocoenose of microscopical organisms the organic matter of which is 

 partially retained, although highly modified through time by very low thermal 

 and metamori)hical alteration. For these reasons the (iunflint chert is uni(|ue 

 among earlier Precambrian sediments in exhibiting the morphological organi- 

 zation of an assemblage of very ancient and primitive organisms, some of which 

 have counterparts among existing primitive group.^ 



JS. 



