Geology of the Muslcingnm Valley. 19 



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almost white color, and shows the formation and mechanical struc- 

 ture of the rock to great advantage. It lies in gently curved waves, 

 such as are produced by a stream of water with a modeiate current 

 flowing over an uneven surilice. So perfect is the illusion, that the 

 observer easily imagines the actual living currents to be passing be- 



an 



the grotto of Plants.* The rock itself or rather this stratum, Is about 

 fifty feet In thickness. It rests on a bed of argillaceous or slaty marl, 

 two feet in thickness. The upper portion is ash colored and very 

 heavy, and the lower portion of the bed, fourteen inches in thickness, 

 is of a deep rich brown, or red. Its structure is slaty, and it splits easi- 

 ly in the line of stratification into thin layers. It is completely fill- 

 ed with vegetable impressions of the most perfect and beautiful 

 structure ; many of them appear to be aquatic plants, but the most 

 abundant are of the genus Neuroptera. If the slaty matrix, w^ere 

 less fragile, very perfect specimens could be procured. As it is, 

 they are, in the hands of any one versed in the botany of fossil plants, 

 sufficient to determine the species. Several figures are given of the 

 plants founJ here, from No. 23 to 26; (pages 10 and 11 of the 

 wood cuts.) No. 23 is one of the most beautiful and perfect branch- 

 es of the arborescent fern that I have ever seen. The foliage is sim- 

 ilar to that represented by M. Ad. Brongnlart in one of his antediluvian 

 trees, as he supposed they appeared when hving. I have seen no 

 similar species, described in his wwk on fossil plants. No. 24, was 

 probably a very porous, thick leaved, aquatic plant, termination 

 ovate ; as fragments of the extremities w^ere found of that shape, 

 cuticle scabrous. The leaf was replaced by a deposit of yellow 

 ochre, one eighth of an inch in thickness, leaving the outlines and 

 markings of the cuticle on the red shale. A large proportion of the 

 plants at the grotto are replaced by yellow ochre. Several other 

 species are impressed on the same fragment. No. 25, is a very 

 rich fern. Each leafliet appears to have been composed ofj or mar- 

 gined by rounded grains, too large and too uniform, for the fruit. 

 The beautiful oblong leaf, No. 26, resembles ^' Neuropteris 

 Scheuchzeri," but is not sufficiently acuminate. Its structure is 

 similar to that of an oleander leaf — and is probably a new species. 

 On the same fragment, are two species of Neuroptera. Pods and 

 seeds of plants, are also common; with the leaf of a thick, aqua- 

 tic plant, like that of the Nelumbium luteum, passing transversely 



* See lithographic Fiontispiece. 



