Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/551

 tradictory nature ; indeed the generic names assigned to the fossils seem to have been given in accordance with their presumed age as determined by the lithological characters and physical conditions presented by the containing rocks, rather than as interpretations of zoological affinities.

Thus the Encrinites which occur in the Nasb-valley limestone are represented by fragments of cylindrical stems, and do not admit of generic determination. The Ammonite, the only fossil mentioned by Figari Bey, is not named specifically ; and I have reason to doubt the correctness of its identification, and suspect that it may have been either a Nautilus or a Goniatite. Mr. Etheridge and Figari Bey have referred the fossils brought under their notice to Secondary genera, Encrinus and Ammonites ; whilst Mr. Salter assigned the Encrinite stems to the Carboniferous genera Rhodocrinus and Poteriocrinus, and adds to the list the Gasteropod genera Murchisonia and Eulima (?), which latter are Triassic as well as Carboniferous.

So that really it has hitherto been difficult to express any very decided opinion on the age of the Nubian Sandstone, owing to the great want of palaeontological evidence. Conclusive evidence of the Carboniferous age of the series, however, has been recently brought to light. Captain Wilson and the Rev. E. W. Holland, of the Sinai Ordnance Survey, have placed in my hands a block of limestone from the Nasb-valley section (vide Bauerman, loc. cit. p. 26) in the hope that it would yield evidence of its age, and so of the associated sandstones.

One fossil only, in a good state of preservation, was contained in the mass ; this I at once named Orthis Michelini, a well-known fossil of the Carboniferous Limestone ; but that the specific determination might be indorsed by the greatest authority on the fossils of the class to which it belongs, and so acceptable as indisputable evidence, I submitted the specimen to Mr. Thomas Davidson, who obligingly writes, that the " inclosed fossil is certainly Orthis Michelini, as you correctly identify it." With this valuable index to the age of the limestone, the obscure forms associated therewith may be approximately assigned to the genera indicated by Mr. Salter, who thereupon referred these beds to the Carboniferous epoch.

Mr. Salter * has moreover described a Lepidodendron from Sinai as a new species, under the name of L. Mosaicum ; and though neither the locality nor the stratigraphical position of the fossil was known to him, yet, as it is preserved in sandstone, we cannot hesitate in referring it to one or the other of the arenaceous members of. the Nubian Sandstone ; and the Rev. F. W. Holland was fortunate in obtaining a portion of a Sigillarian stem from the Wady Mokatteb, which, though not collected in situ, bears unmistakable evidence of having been enclosed in the sandstone forming its cliffs. The sandstone in this valley is overlain by Cretaceous limestone, and is presumably referable to the Upper Sandstone of the Carboniferous series of this region.


 * Quart. Journ. Geol. Soc. vol. xxiv. p. 509.