86 PROCEEDINGS OB* THE GEOLOGICAL SOCIETY. [DcC. 3, 



on the artificial production of vegetable impressions, found that 

 plants of this tribe did, in fact, constantly remain attached to the 

 substance in which they were imbedded, by their lower and not by 

 their upper surface, especially if they were in fructification. 



The carboniferous strata at Frostburg in Maryland, from which 

 these fossils were procured, are described by Mr. Lyell* as being 

 arranged geologically in a trough, and the shape of the successive 

 beds has, he observes, been aptly compared to a great number of 

 canoes placed one within another. The principal coal-seam is ten 

 feet thick ; the coal bituminous, though containing less of volatile 

 matter than what is found farther west on the Ohio. There are 

 numerous smaller seams of coal, under several of which Mr. Lyell 

 found clays containing Stigmaria, " usually, as elsewhere, unaccom- 

 panied by other fossil plants ;" but in one bed of clay, underlying a 

 coal-seam, about fifty feet above the millstone grit on which the 

 whole rests, he found leaves of two species of Pecopteris and an 

 Asterophyllite, intermixed with abundance of Stigmarise. Higher 

 in the series, but still 300 feet below the principal coal-seam, oc- 

 curred a bed of shale full of marine shells, some of which were 

 identical with, and others had a near affinity to, species found in 

 the British coal-measures f. 



The fossil plants procured by Mr. Lyell at Frostburg, in addition 

 to the three ferns already described, were the following :— 



4. Neuropteris cordata. 



(Very abundant, and certainly identical with the English plant. Very variable 

 in size and in the proportional breadth of its pinnae. These are sometimes oblique 

 at the base, nearly as much so as in N. acutifolia of Brongniart, which is proba- 

 bly a variety of this species.) 



5. N. gigantea ? 



(Doubtful ; pinnules as closely placed as in N.flexuosa. It is intermediate in 

 character between N.flexuosa and N. gigantea.) 



6. Cyclopierisl 



7. Pecopteris arborescens, 



8. P. abbreviata ? 



9. p. (?). 



(Perhaps a fragment of P. gigantea or P. punctulata, but too imperfect to be 

 positively determined.) 



10. Lepidodendron tetragonum, 



11 . X. aculeatum, 



1% Lepidodendron 7 ? 



(Resembling in its markings the Sigillaria Menardi of Brongniart, and also the 

 Ulodendron minus of Lindley and Hutton.) 



13. Sigillaria reniformis ? « 



1 4. Stigmaria ficoides. 



15. Asterophyllites foliosa. 



16. A. tubercidata ? 



17. A, equisetiformis? 



* Travels in North America, vol. ii. p. 16-19. ' t Lyell, ibid.. 



