£04 PALEONTOLOGY OF THE EUREKA DISTRICT. 
are preserved in the specimen before us, with a third partially shown; the 
outer ones embrace but little of the inner; they are somewhat flattened and 
apparently sharply rounded on the ventral lobe. Umbilicus wide, exposing 
all the inner volutions. The volutions enlarge very gradually until towards 
the outer portion of the last volution, or the grand chamber, where the ex- 
pansion is slightly increased. ; : 
The entire dimensions of the chamber of habitation are unknown, as a 
portion is broken away and the latter septa are partially concealed by the 
test; the part remaining, however, indicates that it was large. Four septa 
are seen on the outer volution, obtained by cutting away a portion of the 
test; they are thin and uniform, curving a little forward on the umbilical 
margin and then gently curving backward, including a single broad, flat- 
tened lobe which occupies the entire width of the volution. Ventral lobe 
unknown. ‘Test thin. 
Surface marked by strong strize and lines of growth that curve forward 
from the umbilicate lobe, crossing the direction of the septa at an acute an- 
gle near the umbilical margin and nearly at right angles on the outer por- 
tion of the volution. 
This species differs in its wide umbilicus united with the direction of 
the surface strize and septa from any form that has come within our obser- 
vation. 
Formation and locality—WPevonian limestone, Comb’s Peak, Eureka 
District, Nevada. 
CRUSTACEA. 
Genus BEYRICHIA McCoy. 
Beyrichia (Primitia) occidentalis, n. sp. 
Plate xvii, figs. 4, 4a. 
Carapace large, Leperditia-like in outline, 45™™ in length by 2.75™" in 
breadth; strongly convex; dorsal margin slightly incurved two-thirds the 
length of the valves and terminating anteriorly and posteriorly in obtuse 
angles formed by its union with the anterior and posterior margins ; ventral 
margin gently curved to its union with the broadly rounded anterior and 
posterior margins. Two deep and slightly curved sulci penetrate the cen- 
