INTRODUCTORY REMARKS. 5 



ters can be made out from the imperfect specimens) to Upper Silurian as 

 lo Devonian types. The Spirifer, however, is veiij closely allied to forms 

 found in the Upper Helderberg (Devonian) limestones, at the Falls of the 

 Ohio; while the specimens of Atnjpa reticularis belong to a variety very 

 common in rocks of that age in the vicinity of Louisville, Ky., and in the 

 neighboring portions of Indiana. It is also worthy of note, that these fossils 

 were found quite abundant, weathered out of the matrix, and that they are 

 silicified and in all respects similar, in their state of preservation, to the 

 Upper Helderberg fossils, so common in the Western States mentioned 

 above. From these facts, it is highly probable that these Pinon Range fos- 

 sils came from a rock belonging to about that horizon. 



The other Devonian fossils, figured on plates 2 and 3, came from an 

 entirely distinct rock from those mentioned above, and are more than usually 

 interesting, because they were found, with a few exceptions, in the formation 

 containing the rich silver-mines of the White Pine Mining District, Nevada. 

 They were all found in a dark-colored or grayish matrix, entirely different 

 from that containing the Pinon Station fossils mentioned above. Those from 

 the White Pine District consist of several species of Corals, Brachiopods, and 

 two species of Ortlioceras. Among the Corals, there are species that seem to 

 be undistinguishable from the European Devonian forms Acervularia penta- 

 gona and Smithia Hennaliii. The other Corals are an apparently new Alve- 

 olites and a Diphypliyllum* The Brachiopods consist of a small Productus, 

 at least allied to the Devonian species P. stihaciileatus, Atrypa reticularis, a 

 small Hemipronites, apparently undistinguishable from a New York Hamil- 

 ton (jrroup species, and several small Spirifers, some of which resemble Ham- 

 ilton Group forms. 



The presence of the genera Productus and Smithia would alone be a 

 strong argument, in the present state of palseontological science, against the 

 supposition that these silver-bearing beds might belong to the Silurian, to 

 say nothing of the specific affinities of these and the associated fossils; while 

 the occurrence in the same beds of Atrypa reticularis, and the Acervidaria, 

 Smithia, and Ptychophyllum, with the specific affinities of the other fossils, 



*The little Favosites and Gyathophyllum, represented by figures 2 and 3 of plate 

 2, are from a dift'ereut horizon in Arizona. 



