102 PALEONTOLOGY OF THE EUREKA DISTRICT. 



Alveoiites Rockfordensis Haiif 1864. Twenty-third Ann. Rep. ]ST. Y. State Cab. Nat. 

 Hist., p. 229. 



The cell apertures open more directly with the plane of the surface in 

 the Nevada specimens than in those from the Chemung Group of Iowa, but 

 otherwise there la a marked specific similarity and a provisional reference 

 is made to A. Rockfordensis, of the species from Nevada. 



Formation and locality. Upper horizon of the Devonian limestone, on 

 ridge east of Yahoo Canon, Eureka District, Nevada. 

 Cladopora pulchra Ronringer? 1876. Greol. Surv. Michigan, vol. iii, pt. 2, p. 55. 



The Eureka specimens although occurring in the upper beds of the 

 Devonian are closely related to the Upper Helderberg species, C. pulchra, 

 and appear to be specifically identical with it. The obtaining of more and 

 better-preserved examples may prove the two forms to be specifically dis- 

 tinct, but with our present knowledge a separation does not appear to be 

 necessary. 



Formation and locality. Upper horizon of the Devonian limestone, on 

 ridge east of Yahoo Canon, Eureka District, Nevada. 



Cladopora, sp. (und't). 



This is a larger branching form of which worn sections alone have 

 been obtained. It occurs in the central or lower portion of the Devonian 

 formation west of Spring Valley. 



Numerous fragments of an imperfectly-preserved species of Cladopora 

 occur in the silicious Devonian limestone; the stems are usually about 5 mm 

 in diameter and associated with a species of Stromatopora in such quanti- 

 ties as to characterize many beds where other fossils are wanting. 



Thecia ramosa Rominger? 1876. Geol. Surv. Michigan, vol. iii, pt. 2, p. 69. 



This rare and interesting form occurs in the lower portion of the De- 

 vonian, corresponding to its position in the Upper Helderberg limestones at 

 the Falls of the Ohio, and in the State of Michigan. Dr. Rominger 

 describes it as formed of " stout, branching, sometimes reticulated, anasto- 

 mosing stems, from half an inch to two inches in diameter, composed of 

 thick-walled, conico-cylindrical tubes ascending and diverging from a cen- 

 tral imaginary axis. Orifices unequal, of polygonal form, from one to two 

 millimeters wide at the edges of the dilated margins, radiated by twelve 



