6 PALEONTOLOGY OF THE EUREKA DISTRICT. 
considered Cardiomorpha Missouriensis aud fragments of a Spirifera of the 
type of Spirifera Rockymontana Marcou (=S. Keokuk Hall), as probably 
indicating a division of the black shales into Carboniferous and Devonian, 
but, from field observations and the assemblage of fossils, such a division 
is incompatible with the facts. The White Pine shales occupy the same 
position with relation to the Devonian and the Carboniferous systems as 
does the lower portion of the Pogonip limestone to the Cambrian and Silu- 
rian systems. In each case there are beds of passage carrying a fauna that 
unite the faunas of the two systems. 
That the Devonian portion of the White Pine shale fauna is more 
nearly related to that of the shales of the Hamilton Group than that of the 
Chemung horizon, as found in the neighboring Eureka District, is owing 
undoubtedly to the character of the environment of the fauna during the 
deposition of the shales, a feature so well shown in the recurrent faunas of 
the Devonian of New York as studied by Prof. H. S. Williams. 
A summary of the Devonian fauna is given in the following table: 
| Common to Nevada 
| - and— 
| Nevada. SSS SSS 
| | Falls 
| New York.| of Iowa.) 
| | Ohio. | 
Cjass. | A : H j Ailes 
| | a 2 
aah ie) tate 1 
° 
papesee tee | 
| o | o a 5 | 
doce (UR BS Saleem tee eeeallte 
5 a 5 by B = a= pa = 
2 3} 2 2 2A 2 S CS) = 
Ea aon Setlists ear Neral aes 
| & wird} Pp |b to) D nm | 
Poriferays ss atte one eae B | sie at 1 PU eseeran | ee | eens 
OAC TINOZOR ese eenn an eee 1A 127) 15 13 1 11 i 9; 3 
| Roly zm soe - cass cen user 2 3 BY Baste 2a DA Wises etn | Bee ees reat 
| Brachiopoda.-..-.-......- 26/ *883/ 50) 51 18| 26) 38 8] 11 
Lamellibranchiata .-....... 29))' 42))| 227 17 | 2 27 9 2 2 
| .Gasteropoda.............-. 13| 39!) 93| 47 A ates 2 Quon | 
le teropod a)ecesen == cece == 5 8 7 2 1 5 EP ease conc | 
Cephalopoda. - ei) atl 7 4 fi hereae ecko | 
Lon eG peosch ee oes Seeds | 2 | 2 PM aeeace| ke s5e C1 Mpsoee| Sere sels se 
| Peecilopoda.......-.-...--. 4 7 4 Billeseeen 4 Bi oe | 
2 ee a eS Ss ees ee | 
Motalteossanien sceeie- 102 | 225| 141| 108| 24] 94 799|) moh | mien 
| | | 
* And five varieties. 
Of the two hundred and twenty-five species, sixty-one are described 
for the first time, forty-five species are referred to genera but not specifi- 
~ 
