213 



posed of fine, sharp, cjuartz-santT, with a slight admixture of cla}', 

 and occasionally a tiny, silvery flake of mica. The fragments of 

 sandstone lying on the snrface are usually more or less decomposed, 

 and are apt to be stained with iron oxide, which makes them very 

 hard on the outside, while sometimes the surface is covered with a 

 thin layer of the same material. When unaltered the rock appears 

 to be white, or slightly reddish in color. 



The fossils most abundant in the sandstone are the Brachiopoda, 

 which are represented by twenty species belonging to the following 

 genera: Terebratula,VituUna, TropidolejJtus, Spirifera, Crytina(?) 

 Retzia, Streptorhynchus, Chonetes, Orfhis, Rliynchonella, and Lin- 

 (jula, all of Avhich are described in the paper of Mr. Rathbun, 

 annexed. The only other Articulates are the trilobites which are 

 represented by a beautifnl Dahnania that occurs in abundance, 

 and a sj^ecies of Ilomalonotus, of which last only a fragment is 

 known. 



Several species of Lamellibranchs occur in the sandstone, belong- 

 ing to NucuUtes, Palaeoneilo, Grammy sia (f), Edmondia, and one or 

 two other genera. The Gasteropods number about eight species, 

 representing the genera Belhrophon, Platyceras, Holopea, PUuroto- 

 maria and TentacuUtes. A few fragments of crinoid stems have 

 been found, together with a numl)er of obscure markings Avliich 

 may be of plants. 





Jf-^, 





\n-. 





Serra of Erere from the North. 



This fauna has an unmistakable Devonian facies, but it is diffi- 

 cult to determine its exact ecpiivalency. In some features, as for 

 instance in Spirifer Pedroana, which closely resembles ;S'. varicosa, 

 the fauna recalls that of the Corniferous, wiiile in the occurrence 

 of Tropidoleptus and Vitulina it approaches the Hamilton.* 



* See concluding remarks to Mr. Riithbun's paper. 



