FOSSILS OF THE DEVONIAN. 119 
Strophomena (Strophodonta) demissa Hall, 1857. Tenth Ann. Rep. N. Y. State Cab. Nat. 
Hist., p. 137. 
Strophodonta demissa Hall, 1858. Geol. Iowa, vol. i, pt. 2, p. 495, pl. iii, fig. 5. 
Strophomena demissa Billings, 1861. Canadian Jour., vol. vi, p. 341, figs. 116-118, 
demissa Billings, 1863. Geology of Canada, p. 367, figs. 377a-d. 
Strophodonta demissa Hall, 1867. Pal. N. Y., vol. iv, pp. 81, 101, and 114, pls. xi, xii, 
Xvii, xix. 
Strophomena (Strophodonta) demissa Meek, 1868. Trans. Chicago Acad. Sci., vol. i, p. 87, 
figs. 6a-c. 
Strophodonta demissa Nicholson, 1873. Pal. Prov. Ontario, p. 65. 
demissa Whitfield, 1883. Geol. of Wisconsin, vol. iv, p. 327, pl. xxv, fig. 18. 
This species in New York occurs throughout the Devonian. It has 
also been found in Illinois, Iowa, and to the far Northwest, in the Mackenzie 
River Basin In the Eureka District it is restricted, as far as known, to 
the Lower Devonian horizon. The specimens are below the average size 
of those from the Hamilton Group of New York, corresponding in this 
respect to the Upper Helderberg form; they are also more finely striated. 
Formation and localities —Lower horizon of the Devonian limestone, 
midway of Gray’s Cation, Eureka District, and at Lone Mountain, 18 
miles northwest of Eureka, Nevada. 
Strophodonta Patersoni Hall. 
Strophomena (Strophodonta) patersoni Hall, 1857. Tenth Ann. Rep. N. Y. State Cab. 
Nat. Hist., p. 114. , 
Strophomena Patersoni? Billings, 1861. Can. Jour., vol. vi, p. 340, fig. 115. 
Strophodonta patersoni Hall, 1867. Pal. N. Y., vol. iv, p. 89, pls. xii, xiii. 
Strophomena Patersoni Nicholson, 1873. Pal. Prov. Ontario, p. 67. 
There is but one specimen of the ventral valve of this species in the 
collection, but its depressed convex form, arching wrinkles between the 
coarser striz, and the fine intermediate radiating strie give it all the promi- 
nent characters of the species. In New York and Canada, S. Patersoni is 
an Upper Helderberg species, not being known in the Hamilton or Chemung 
Groups. Its horizon in New York and Canada is the equivalent of the 
Lower Devonian horizon in the Eureka District. 
Formation and locality—Devonian formation, lower horizon, Lone 
Mountain, 18 miles northwest of Eureka, Nevada. 
