TO JUNCTION OF (IRANI) AND GKEEN KIVKRS. 49 







Feet. 



3. Foliated micaceous sandstone, generally gray, but often brownish-red, with 



very smooth surfaces ; the red portions presenting precisely the lithological 

 characters of the brown freestone of the Northern Atlantic States. The 

 lighter portions more compact, containing many impressions of vegetable 

 stems and small branches of Walrhia f 11 . 



4. Chocolate and greenish micaceous shales 18 



5. Purplish-gray conglomerate, quite hard, containing much peroxide of iron. . . 10 

 (j. Purple and green shales 30 



7. Conglomerate, with masses of peroxide of iron and copper 9 



8. Purple and green shales to covered slope 20 



At Pecos, on about the same level geologically with the stratum containing the 

 vegetable remains of the preceding section, I found the surfaces of slabs of red sand- 

 stone marked with impressions of a large and handsome fern, evidently a Pccopteris, 

 but too imperfect for specific determination or description. There is no doubt that, 

 with more time than I had at command, fossil plants would be found in the valley of 

 the Pecos, which would throw much light upon the geological age of the lower divi- 

 sion of the Gypsum formation. Those which I obtained are insufficient to decide any 

 of the questions which have been raised in regard to the parallelism of the beds con- 

 taining them with those of other countries, while they may perhaps justly afford 

 ground for a suspicion that the classification which refers all the Gypsum formation to 

 the Trias may be in part erroneous. Calamites are ordinarily of little value in deter- 

 mining nice points of geological parallelism, and the specimens here obtained are few 

 and imperfect. The same has been said of the ferns. The Walchia however, if 

 undoubtedly such, would afford good evidence that the strata which contain it should 

 be classed with the Permian of Europe, as that genus, as restricted by Brongniart, is 

 confined to the Permian and older formations. But in the Trias, Walchia is succeeded 

 and represented by Voltzia, a closely allied conifer, so similar that imperfect specimens 

 of the two genera are not readily distinguishable; and until more and better specimens 

 can be procured from the Pecos Valley, I should scarcely be justified in saying that 

 the plant to which I have referred is a Walchia of Permian age, and not a Volteia, an 

 evidence of the Triassic date of the rock containing it. The specimens before me, 

 however, have all the characters, so far as preserved, of the Walchias, but exhibit none 

 of the cones, which wcmld be decisive. The branchlets are closely approximated, 

 pinnate and parallel,, covered with small falcate or subulate, acute leaves, apparently 

 more acute and less fleshy than the smaller leaves of Voltzia heterophylla, or even V. 

 acutifolia. There is also, apparently, no tendency of the foliage to assume the dimor- 

 phous character so marked a feature in the Voltzias. If a Voltzia, it is evidently a new 

 species, quite distinct from those of Europe. Until farther information can be obtained 

 in reference to this plant, I am disposed to regard it as a Walchia, and as very similar 

 in its general aspects to W. Schlotheimii of the schists of Lodeve. By Messrs. Unger 

 and Endlicher the genus Walchia is not recognized, its species being placed by these 

 authors, as formerly by Brongniart, in Lycopodites. Sternberg, and more recently 

 Brongniart, have, however, regarded it as distinct, and the latter author compares it with 

 the Norfolk Island pine (Araucaria excclsa). 



7 S F 



