112 PALEONTOLOGY OF THE EUREKA DISTRICT. 



Genus DISCINA Lamarck. 



Discina toiuuta Hall. 

 Plate xiii, fig 5. 



Orbicula minuta Hall, 1843. Geol. Rep. Fourth District of New York, p. 180. 

 Discina minuta Hall, 1867. Pal. N. Y., vol. iv, p. 16, pi. i, fig. Wa-b. 



This small and pretty species is represented by a number of examples 

 that correspond closely with the typical specimens from the Marcellus shale 

 of New York, and which are considered identical with them, although 

 separated by a distance of 1,800 miles, and occurring at a different horizon 

 in the Devonian Group. 



The New York specimens vary from 1.5 mm to 4 mm in diameter, while 

 the largest from Nevada is 4 mm in its greater diameter, and of about the 

 same convexity as examples of the same size from New York. 



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

 The G^te, northeast of Eureka, Nevada. 



Discina, sp. (T) 



Considerable interest is attached to this shell, as it is very rare and 

 the only species of the genus from the Lower Devonian of the Rocky 

 Mountain area, but one imperfect specimen showing the two valves united 

 occurs in the collections. In general form it is not unlike Discina media of 

 the Hamilton Group of New York. 



Formation and locality. Lower Devonian of Lone Mountain, 18 miles 

 northwest of Eureka, Nevada. 



Discina Lodensis Hall. 

 Plate ii, figs. 5, 5 a. 



Orbicula lodensis Hall, 1843. Geol. Rep. Fourth Dist. N. Y., p. 223. 



lodensis Vanuxem, 1842. *Geol. Rep. Third Dist. N. Y., p. 168. (Wood cut 



used in advance of publication of the Report on the Fourth District*) 

 Discina lodensis Hall, 1867. Pal. N. Y., vol. iv, p. 22, pi. i, figs 14 a-f; pi. ii, fig. 35. 

 lodensis Rathbun, 1874. Bull. Buflalo Soc. Nat, Sci., vol. ii, p. 257. Ibid., 1878 



Proc. Boston Soc. Nat. Hist., vol. xx, p. 17. 

 Compare D. media Hall, 1857. Pal. N. Y., vol. iv, p. 20, pi. ii, figs. 25-28. 



