FOSSILS OF THE DEVONIAN. 



107 



-essential particulars. It is a rare species, both in the Hamilton Group of 

 New York and the lower horizon of the Devonian formation at Lone Mount- 

 ain, 18 miles northwest of Eureka, Nevada. 



Dimensions: length, 17 mm ; greatest breadth, 12 mm . 



Lingula Ligea Hall. 



Plate ii, fig. 2. 



Lingula ligea Hall, 1860. Thirteenth Ann. Eep. N. Y. State Cab. Nat. Hist., p. 76. 

 Ibid., 1867. Pal. K Y., vol. iv, p. 7, pi. i, tig. 2 a, &; pi. ii, fig. 8. 



This pretty and symmetrical little shell is represented by one specimen 

 that in external appearance is identical with specimens pf L. Ligea now before 

 me, from the Hamilton Group of New York. 



In a layer of limestone, about M) feet above that containing the above- 

 mentioned shell, a number of examples of a form that may be only a varia- 

 tion of L. Ligea were collected. In as close a genus as Lingula, however, 

 this variation is unusual, and a varietal distinction is made. 



Lingula Ligea var. Nevadeiisis, n. var. 

 Plate ii, fig. 3. 



Shell below the average size of L. Ligea, and with more rounded sides 

 and pointed beaks than that species. 



Surface marked by fine concentric stria? of growth. 



The interior of the ventral valve shows the path of advance of two 

 central muscular scars, and also a iateral scar on each side. The impres- 

 sions of the scar are too faint to be of any service in determining their 

 character or number. 



Formation and locality of this and the preceding species, Upper Devo- 

 nian of Rescue Hill, Eureka District, Nevada. 



A species undistinguishable from this occurs in the Lower Devonian of 

 the south slope of Sentinel Mountain, Eureka District, Nevada. 



