National Academy of Sciences. 



19 



portion of the Cincinnati croup, near Lebanon, Ohio. 

 These ho considers as the remains of hind plains, and 

 refers them to ttte genus Sigillnria ; and this case is 

 Cited as the. first instance whero plants so highly 

 organized have been met with in Lower Silurian rocks. 

 Through the kindness of the Rev. H. Hertzcr, to whom 

 the specimens in question belong, they had been in my 

 possession some time before the publication of Mr. 

 Lesquereux's notice, and I had examined them with 

 some care for the purpose of determining, if possible, 

 their botanical relations. I had also made careful 

 drawings of them, of which copies are herewith sub- 

 mitted. As the result of my examination I am 

 compelled to say that I fail to find either 

 in the external characters or internal struc- 

 ture of these specimens any satisfactory evidence 

 that they represent land planes; still less that 

 they form species of the genus Siyillaria. Their 

 external markings are fairly represented iu the accom- 

 panying figures, and 1 am compelled to say that they 

 exhibit no internal organic structure whatever. They 

 are simply casts in earthy limestone without carbon, 

 aceotis matter, or any traces of woody tissue. The 

 smaller specimen is a discoid section of a cylindrical 

 trunk of which the external surface is very smooth, but 

 is marked by a reticulation not unlike that of one 

 section of the genus Sifjillaria. I fail to find, 

 however, any dots or tubercles in the 

 centers of the meshes, such as are referred to by Mr. 

 Lesquereux, and which were they present might be 

 supposed to represent the place of the nutrient vessels 

 of the leaves. Taken by itself I should say that this 

 specimen might bo considered to represent a sponge or 

 some other low form of marine life, quite as well as 

 Slf/illaria. Since the specimen is so small and forms so 

 little of the original organism I think it would be unsafe 

 to make it the base of any general aud important con- 

 clusion. 



The layer specimen is represented, like the other, 

 of the natural size. Tuis is also a cast of 

 a nearly cylindrical trunk of which the ex- 

 ternal surface is roughened by irregularly disposed 

 and unequally sized lenticular prominences. These re- 

 call, in a rude way, the leaf scars borne by the trunks ot 

 some Lveopodiaceous or Cycadaceous plants, but they 

 do not exhibit the spiral arrangement, nor the details of 

 structure which the leaf-scars of such plants almost uni- 

 versally retain in the fossil state. In the interior of this 

 trunk are seen a fovv irregularly scattered points of car- 

 bonaceous matter, but they are not contiuous fibers, and 

 to ray eye show no traces of cell structure. 



Taking all the characters of these interesting fossils 

 into consideration, I am disposed to regard them as 

 casts of the srems of fucoids. Hud they been lanu plants 

 they would almost certainly exhibit more distinctness 

 and regularity of surface marking, some coating of car- 

 bonaceous matter, aud some tr.ices of organic structure. 

 A large number of specimens of sea-floated hind plants, 

 which we have found in the Djvoni.m limestones of 

 Ohio, all assert their botanical affinities by these 

 characters. The remains of fucoids, on the con- 

 trary, consist almost universally of mere casts 

 of their external surface, carbonaceous matter 

 nnd internal structure having both entirely disappeared. 

 For these reasons, therefore, I should hesitate to hang 

 npou these specimens so important a conclusion as that 

 promulgated by Mr. Lnsquereux. I would not be under- 

 stood, however, to assert positively that they are not 

 the remains of land plants, for they are too imperfect 

 to be decisive of that question, but ouly this, that they 



do not afford characters which permit one to accept them 

 as evidence of tiie existence, ofland plants, and certainly 

 not of Slyillariti, in Ohio, during the Lower Silurian 

 age. The remains of what hava been called land plants 

 are found in the Lower Cambrian sandstones of Sweden, 

 and two species have been described (K.^iln/im, ;.,-nnitr- 

 sonum, Torell, and E. Torelli, Lenarson). Thesis plants 

 are pronounced by algologists not to bo alga}, but are 

 referred to vascular cryptogams aud monocotyledons. 

 It is not certain, however, that they arc not tliallogens. 

 as all traces of structure are lost, and nothing is k>ft 

 but the cast or impression of the external surface. 

 (Geological Magazine, September, 18G9.) 



Lana plants of Gaspe have also been found in tho 

 Upper Silurian strata, Canada, by Prof. Dawson. Hero, 

 with a large number of fucoids, a few specimens have 

 been found.which he refers to his genus Psiloplayton. In 

 these the scalariform axis, and the outer fibrous back 

 both remain aud serve as satisfactory guides in their 

 classifica'ion. (Dawson' 's Prccarboniferons Plants of 

 Canada, p. CG.) 



With these exceptions no land plants are reported 

 below the Devonian. On this point, however, the evi- 

 dence is all negative, and highly organizsd land plants 

 may be nt any time found in the Lower Silurian rocks. 

 Indeed, the variety and high rank of the Devonian flora 

 prepares us to expect such, a result. Strict accuracy 

 compels us to state, however, that up to the present timo 

 positive proof of the existence of land plants in the 

 Lower Silurian has not been met with in other countries, 

 nor is it furnished by the specimens under considera- 

 tion. What we know of tho physical condi- 

 tion of the region about Cincinnati during 

 the Lower Siiurian age strengthens the conclusion 

 that the specimens before us are the remains of marine 

 and not terrestrial vegetation. As I have shown in the* 

 Geological Report of Ohio, the Cincinnati axis was raised 

 above the sea at the close of the Lower Silurian age, 

 and when the Cincinnati group was deposited an open 

 sea occupied all that region. The shores of this sea 

 were formed by the Eozoic highlands about 

 Lake Superior, in Canada, in the Aiiiroudacks, 

 arid along the Blue Ridge; nowhere less than 

 000 miles away from the locality where 

 these fossils were found. It becomes, therefore, ex- 

 tremely improbable that two distinct species of terres- 

 trial plants should bo wafted from thoso distant shores 

 and deposited in the calcareous sediment of the sea at 

 this point. The remains of fucoids are, however, not un- 

 common in the Cincinnati group, and the only objection 

 to grouping these fossils with BulhotrcpJns aud the 

 other Silurian algae must be found in their some- 

 what peculiar surface-markings. These are, how- 

 ever, not unlike the markings on tho stems 

 of many recent and fossil fucoids. Tho summit 

 of the stem of the tri.mt kelp Macrocystis is n> irkt il with 

 irregular rings left by the removal of their great fronds, 

 and the stems of many fossil fucoiJs are scaled or tuber- 

 culated more regularly and distinctly than are these 

 specimens. Among such I will only cite Arthrophycut 

 nullii of tho Medina, the tuberculatcd fucmd railed 

 Ifalt/nicmtisot the Cretaceous, and the scaled Phytodcrma 

 of the Jurassic. 



HOW THE EARTH WAS FORMED. 



BY CAI'T. C. E. DTJTTOX, U. 8. A. 



This paper w:is entitled A Criticism upon 



the Contractional Hypothesis. 

 The hypotheses that have been put forward to 



