S PALEONTOLOGY. 



among the specimens from that rock, fragments of an Archimedes, together 

 with imperfect specimens of Spiriferina spinosa* (both Lower Carboniferous 

 types), it is very probable that this rock belongs to the Lower Carboniferous 

 series. This view also receives some support from the presence, in these 

 dark beds, of a species of LitJiostrotion, a genus very abundantly represented 

 by one or two species in the Lower Carboniferous, but unknown in the Coal- 

 Measures of the Mississippi Valley. 



When we turn our attention to the fossils from the light-yellowish Car- 

 boniferous limestones of Nevada, however, at the localities mentioned, we 

 find among them forms undistinguishable from Athyris suhtilita, Spirifer 

 cameratus, Froductus Prattenianus, and Spiriferina KentucJcensis-,'^ none of 

 which are certainly known from any horizon below the Coal-Measures of 

 the Mississippi Valley. Hence it is more probable that these lighter-colored 

 Carboniferous limestones belongto the horizon of the Coal-Measures; though 

 I believe no beds of coal have yet been found associated with them. 



Perhaps of all the collections of fossils that have yet come to us from the 

 Far West, there are none more interesting than those from the Upper Trias of 

 West Humboldt Range. The specimens from this formation in the collec- 

 tions under consideration are illustrated on plates 10 and 11, and will be 

 seen to consist of a few bivalves and some ten or twelve species of Cephalo- 

 poda. The occurrence of this formation in that region was first made known 

 by Prof. J. D. Whitney and Mr. Gabb, of the California Geological Survey, 

 in the reports of which several of the species here figured were illustrated 

 and desoribed along with others. 



It is a remarkable fact that there should be at these distant western locali- 

 ties an immense series of deposits, containing so exact a representation of 

 the very peculiar fauna of the Upper Trias of Europe, as exhibited in the 

 St. Cassian, Aussee, and Hallstadt deposits. For instance, there are, among 

 the collections that have been by different parties found in these beds, the 

 following peculiar genera, especially characteristic of the rocks of this age 

 in Europe, viz., Halohia, Monotis, CassianeUa,f Trachjceras, Archestes, Clido- 



* The specimens of these species in the collection, although recognizable, are not 

 in a condition to be figured. 



t Mr. Gabb has described a species of this genus in the American Journal of 

 Conchology from this formation in Nevada. 



