306 PROCEEDINGS OF THE CALIFORNIA 



ance of a difficulty, I leave to others to decide. It is far easier to ignore such 

 a difficulty than it is to explain it away. 



In regard to the distribution of the genera and species in this and the associated 

 rocks. All of the species are peculiar to this group, or to this and underlying 

 rocks ; not one has been found associated either with living forms, or with spe- 

 cies known to occur in the recognized Tertiaries of California. Five of the 

 genera are peculiar to the Secondary. An Ammonite ranges entirely through 

 the group to the top of the highest fossil iferous strata. The genera Perissolax, 

 Gyrodes, Margaritella, and the sub-genus Anchura, of the genus Aporrhais, are 

 all recognized as strictly characteristic of the Cretaceous ; so much so, that the 

 presence of a single undoubted representative of either of these genera would 

 be strong presumptive evidence of the Cretaceous age of any rocks in which it 

 might be found. On the other hand, the presence of such genera as those in 

 the list given below, would point to a very modern era in the Cretaceous, to 

 say the least. 



It must be borne in mind that we have much to learn yet in paleontology, 

 especially in the matter of the vertical range of genera. Every year we find 

 genera, nay, whole families, extending themselves beyond what had been fixed 

 by previous authors as their limits. A few years ago, the presence of mammal 

 ian remains was considered characteristic of the Tertiaries. Now we know 

 of Marsupials in the Trias, and who dare say that we cannot find mammals in 

 palaeozoic rocks? I therefore maintain, that though we have here such genera 

 as' Aturia, Typhis, Cordiera, Pseudoliva, Nas.^a, Mitra, Ficus, Morio, Cerithiop. 

 sis, Cypraea and Galeru?, still, the only inference that can be drawn is, that the 

 group is on or near the verge of the formation, a sort of prophetic member, 

 presaging by some of its genera the formations to come, but indissolubly 

 bound by specific ties with thr> eras preceding. 



Prof. Blake stated that he considered the collections made by 

 him, in and near the Canada de las Uvas, as not meager. There 

 was a sufficient number of species to make a quarto plate of 

 figures. 



Prof. Blake read the following notice : 



Fossil Fish in the Great Basin, Nevada. 



BV WM. P. BLAKE. 



Fossilized fish are found in a light-colored clay shale, in the mountains a few 

 miles north of Silver Peak, a mining district in the Red Mountain or Salt 

 Basin region, about one hundred and fifty miles south of Austiu. The verte- 

 bral columns, ribs and fins are very distinctly shown, and the specimens are 

 exceedingly interesting. They remind me of the specimens from the famous 

 locality of Mount Bolca, in Europe. The specimen that I have here, does not 

 appear to belong to an ancient period, but I will not venture to refer it without 



