63 



We may note the almost universal extermination of genera at the 

 close of the Carboniferous, marking the grand division between Pal- 

 aeozoic and Mesozoic times. The types of the Mesozoic are more 

 highly organized forms than those of the Carboniferous. The great 

 physical and climatic changes which influenced the organic changes; 

 and the immense lapse of time of which no record is found. To 

 these more general facts, now add the striking and very important 

 one that no Lepidodendron has ever been found in the upper coal- 

 measures, where other vegetation of similar habits is abundantly pre- 

 served. Another point is, that Sigillaria^ a plant of higher structure 

 and affinities than Lepidodendron^ and which continued to the end of 

 the Carboniferous, has never afforded a specimen of later age. More- 

 over, the life of the Trias is comparatively well known, and plants in 

 considerable abundance have been found in many Triasslc areas in 

 different parts of the world. 



Although the objections to Triassic Lepidodendron are so evident 

 and forcible, we nevertheless must admit that the improbability does 

 not decide the question. But the evidence as to the nature of the 

 fossils should be in the highest degree clear and incontrovertible to 

 justify such a reference as the one under consideration, in opposition 

 to all experience and probability. 



Upon what facts or reasons, then, is this determination really 

 based ? Merely that the surface of the fossils is covered with irreg- 

 ular rhomboidal areas. These have of necessity a spiral arrange- 

 ment, and, in this respect, but in this alone, resemble imperfectly pre- 

 served Lepidodendron, They possess none of the characteristic inter- 

 areal markings^ the sure test of that genus. If the fossil were found 

 in the coal-measures one would be justified in supposing it to be a 

 decorticated Lepidodendron, But some cycads have similar mark- 

 ings, and so have many conifers, as Araucaria, And why not Mes- 

 ozoic conifers or cycads, the characteristic plants of that era ? Or, 

 as yet more probable than Lepidodendron^ why not some unknown 

 group of plants related to, or superficially resembling Lepidodendron 1 



That the fossils in question belong to some one of these groups 

 is vastly more probable. And the reasons for the determination are 

 certainly insufiicient to sweep away all the weight of objection and 

 bridge the great gap between the life of the Palaeozoic and Mesozoic. 



Secondly, the specific determination is even less well founded. Z. 

 Veltheimianu7?i^ is admitted to be characteristic of the Devonian and 

 Sub- Carboniferous the world over, with not a single undoubted spec- 

 imen from the coal-measures. Yet in the coal-measures it ought 

 surely to be found if it had then existed. Not to find it in those de- 

 posits, filled with similar plants, which cover so wide and scattered 

 areas, and represent such a duration of time, is to be almost certain 

 of its extinction. The same reasoning applies to this which applies to 

 the absence of all Lepidodendron from the upper coal-measures. 



No one would claim that all Carboniferous species have been dis- 

 covered. But that an arborescent lycopod could have a world-wide 



*The old authorities credit the species to Sternberg and not to Presl, (I judge 

 the spelling of the author's name in the quotatipn is a typographical error) and 

 spell the specific name with V as initial. 



