1892 .] On Problematic Organisms. 9 



and he reached the conclusion that marine plants are only 

 rarely preserved in a fossil state. He based his deductions of 

 past conditions upon present ones ; and lie noted that alga 1 are 

 at the present time scarcely ever found in any good state of 

 preservation. "The difference," he says, "between the woody 

 or vascular tissue of land plants and the cellular compound of 

 the marine or fresh-water alga, more filaments glued together, 

 or imbedded in vegetable mucus or gelatine, explains at once 

 whv the remains of fucoids are so rarely found petrified.' 

 Further he says : "Nowhere have I been able to find any 

 trace of a deposit of sea-weeds preserved from decomposition 

 under any kind of superposed materials, sand, clay, etc. And, 

 nevertheless in some of the countries visited, the shores in 

 many localities are strewn with immense heaps of those plants 

 thrown out by the waves. Marine vegetables, though they 

 may appear of hard, leathery texture like most of the common 

 species of Fucus, soon disintegrate, and pass into a gelatinous, 

 half-fluid matter, which penetrates the sand, so that the lowest 

 strata of these heaps when exposed to atmospheric action, do 

 not generally preserve traces of their organism for more than 



While Lesquereux thus announces his positive belief, Mr. 

 G. F. Matthew says that while the alga? buried in sand leave 

 no trace, " in clay the result is different. In the Till and Leda 

 Clays of the Acadian coast, which have considerable antiquity, 

 the writer has seen Polysiphonias and other delicate sea-weeds 

 as well preserved as the ferns and Asterophyllites of the shales 

 of the Carboniferous system/' 



It is generally acknowledge.! that organic remains are more 

 likely to be preserved in an area of subsidence than in one 

 that is stationary or rising. Sediment is rapidly accumulated 

 in the first, and animals living in the vicinity are likely to be 

 preserved. It is also probable that animals living on or near 

 the bottom of the ocean have a better chance of being entombed 

 than those floating in the water, so that a certain depth of 

 water and a comparatively rapid accumulation of sediment 

 seem to be two necessary adjuncts for the preservation of or- 

 ganisms in anything like abundance or perfection. The so- 



