562 Prof. E. W. Clay pole — Fossil Tree from the U. Silurian. 



same Journal, on these specimens, says : — " They had been in my 

 possession some time before the publication of Mr. Lesquereux's 

 notice, and I had examined them with some care, and had also made 

 careful drawings of them. As the result of my examination, I am 

 compelled to say that I fail to find either in the external character 

 or internal structure of these specimens any satisfactory evidence 

 that they represent land-plants — still less that they form species of 

 the genus Sigillaria." " They are simply casts in earthy limestone, 

 without carbonaceous matter or any traces of woody tissue." 



In the " Eeview of the Fossil Flora of North America," 1876, 

 Ml*. Lesquereux says : — "A few cylindrical branches or impressions 

 of branches upon clay, bearing upon their surface rhomboidal scars, 

 disposed in spirals around the stem, like those of Lepidodendron, 

 were lately discovered in the Cincinnati group of the Middle 

 Silurian. As they were found associated in the same strata with 

 fragments of fucoids and deep-marine Molluscs, their relation was 

 considered as being rather with peculiar forms of Alga3." 



But in the paper above mentioned, 1877, Mr. Lesquereux reasserts 

 the terrestrial nature of these specimens, and describes them under 

 the name of Protostigma sigillarioides. The genus is thus defined. 

 " This generic name is provisionally admitted for the description of 

 fragments of stems, whose relation to species of Sigillaria, etc., is 

 surmised from the rhomboidal form of their scars." He adds, in 

 the introduction, that Professors Dana, Eaton, and Yerrill all agree 

 in referring the remains to land-plants. "Where such distinguished 

 authorities, with the advantage of having seen the specimens, ex- 

 press such opposite opinions, the matter must be considered at least 

 doubtful. 



Mr. Lesquereux also describes, in the same paper, two other 

 specimens from the Cincinnati group. The former of these he names 

 Sphenojphyllum primcevum, and the latter Psilophyton gracillimum. 

 The opinion of so eminent and experienced a palseo botanist is 

 entitled to the greatest respect, and the discovery of fossil land- 

 plants of Lower Silurian age in some parts of America is by no 

 means an improbable event. It is right, however, to observe that 

 the latter of these is a fossil long known to collectors in this part 

 of the country, and by them always considered to be identical with 

 Graptolitlius abnormis, Hall, from the Quebec Group of Canada. 

 This alone will show how much uncertainty as yet attends the 

 identification of the fossil. In regard to both the species just named 

 serious difiiculties also arise from a consideration of the physical 

 geology of the region at the time in question, against too ready a 

 conclusion in favour of their terrestrial origin, and especially against 

 the probability of their occurrence near Cincinnati. During the 

 existence of the Cincinnati Ocean of Lower Silurian date, the whole 

 of the interior basin was under water. The nearest shores were 

 the Blue Eidge of the Appalachian chain, on the east, 500 miles 

 from Cincinnati — the Laurentian highlands, on the north, at about 

 the same distance — the Huronian (?) highlands of Michigan, to the 

 north-west — the present site of the Eocky Mountains, to the west — 



