The American Naturalist 



Two subjects of primary importance need to be discussed 

 before any detailed examination of these problematic organ- 

 isms can be made. These are: — I. — Absence of organic or 

 carbonaceous matter. II. — Probability of the preservation of 

 algee. 



I. — Absence of organic or carbonaceous matter. 



The absence of organic* matter in the fossil bodies under 

 consideration makes it difficult to decide in many cases what 

 they really are. Their mode of occurrence is usually on the 

 under side of the strata as objects in relief. They are mostly 

 of indefinite and quite variable form, so it is scarcely possible 

 to find any two alike in details. Not only are organic form 

 and organic substance absent, but the beds in which the greater 

 part of the bodies occur are strikingly deficient in organic re- 

 mains of any other kind, and while these may be and are 

 abundant in strata hot li above and below, the beds themselves 

 are nearly barren of any but the problematic fossils. 



The absence of carbonaceous matter has been considered by 

 some a strong argument against the vegetable nature of the 

 remains; while the presence of it has, conversely, been re- 

 garded as indicating an undoubted Vegetable origin. Bui on 

 the one hand we know of organisms, of unquestioned animal 

 origin, in which not a trace of organic matter is left, the im- 

 pression or cast alone remaining ; and we likewise know of 

 unquestioned vegetable remains which are also m the form of 

 casts; but which are so perfectly preserved that even the deli- 

 cate venation can be studied and described. 



On the other hand there are forms of animal origin, like the 

 graptolites.in which there is abundant evidence of the presence 

 of carbonaceous matter, just as there is in true plants, and sonic 

 of the graptolites were originally referred to the vegetable 

 kingdom on this account. So that it can sea reel v be con- 

 sidered that the presence of carbonaceous matter makes the 



vegetable nature. But, when the absence of definite form, of 

 carbonaceous matter, of other organisms in the same beds of 

 rock, and their occurrence in demi-relief on the under side of 

 the strata; when all these are taken into eonn-leration it can 



