FOSSILS OF THE DEVONIAN. 115 
Orthis impressa Hall. 
Plate xiii, fig. 13. 
Orthis impressa Hall, 1843. Geol. Rep. Fourth District of New York, p. 268 and p. 267, 
impressa eset Pal. N. Y., vol. iv, p. 60, pl. viii, figs. 11-19. 
impressa Whitfield, 1883. Geol. of Wisconsin, vol. iv, p. 326, pl. xxv, figs. 13-15. 
Compare 0. Tulliensis Vanuxem, 1842, Geol. Rep. Third District, New York, p. 55. 
O. Towensis Hall. 1858, Geol. Surv. Iowa, vol. i, pt. 2, p. 488, pl. ii, figs. 
4 a-i,and O. Me. Farlanei, Meek, loc. cit., p. 114. 
In New York this species is found in the Chemung Group, and is re- 
garded by Professor Hall as closely allied to Orthis Tulliensis, of the Tully 
limestone, which occurs about 1,000 feet lower in the strata, no species of 
Orthis being known in the interval. In Nevada the relative position of the 
two forms is somewhat reversed; QO. impressa is found only at the base of 
the Devonian, and 0. Tuiliensis at the base and near the summit, 4,000 feet 
above. 
A comparison of the Chemung specimens from New York with the 
Nevada examples shows a most perfect identity between them, while the 
O. Tulliensis is quite as decided in its characters as in New York. Associated 
with O. impressa, at Lone Mountain, there is a more convex form that is of 
the type of 0. Tulliensis, and it may be referred to it. 
Formation and localities—Lower horizon of the Devonian limestone, 
Comb’s Peak; 2 miles east of Castle Mountain; west slope of County 
Peak, and Lone Mountain, 18 miles northwest of Eureka, Eureka District, 
Nevada. 
Orthis Tulliensis Vanuxem. 
Plate ii, figs. 12, 12a, 
Orthis tulliensis Vanuxem, 1842. Geol. Rep. Third District New York, p. 164 and fig. 
2, on p. 163. 
tulliensis Hall, 1867. Pal. N. Y., vol. iv, p. 55, pl. vii, figs. 5a-k. 
Compare O. Towensis Hall, 1858. Geol. Rep. Iowa, vol. i, pt. 2, p. 488, pl. ii, figs. 4a-7. 
The facts connected with the distribution and range of this species have 
been mentioned in the notes of the preceding species. ‘The specimens from 
The Gate, northwest of Eureka, are not quite as gibbose as the majority 
