FOSSILS OF THE DEVONIAN. 7a 
In general appearance this shell resembles a Nuculites or Palzeoneilo, 
but it is without the clavicular ridge of the former and the faint muscular 
scars of the latter. In the presence of the strong anterior muscular scar, 
the somewhat nasute anterior end and the rounded up posterior extremity 
it is allied to Dystactella subnasuta, Hall (Pal. N. Y., vol. y, pt. 1, Plates and 
Explanations, p. 14, pl. li, figs. 28-31, 1883) from the Upper Helderberg 
rocks of the Falls of the Ohio. 
Formation and locality—lLower part of the Devonian limestone in the 
lower or central area of Gray’s Canon, Eureka District, Nevada. 
Genus MEGAMBONIA Hall. 
Megambonia occidualis, n. sp. 
Plate v, fig. 1. 
Outline subcireular. Length and breadth subequal. General sur- 
face strongly convex, with a convex anterior wing separated from the 
body of the shell by a well-marked, slightly curved sinus. Hinge-line 
shorter than the width of the shell. 
Right valve unknown. Left valve with the beak depressed and cury- 
ing forward over the cardinal line. Area and interior characters unknown. 
Surface marked by strong concentric striz and lines of growth; a few 
radiating lines are shown in the posterior half of the shell. 
The most nearly related species is Megambonia subcordiformis Hall 
(Pal. N. Y., vol. v, pt. 1; Plates and Explanations, pl. lii, figs. 1, 8). The dif- 
ferences are the less elongate form and the character of the surface markings. 
Formation and locality—lLower Devonian; Lone Mountain, 18 miles 
northwest of Eureka, Nevada. 
Genus NYASSA Hall. 
Nyassa parva, 0. sp. 
Plate xv, figs. 14, 14a. 
Shell small, transversely elongate, with the cardinal and basal margins 
subparallel, the posterior end being a little broader than the anterior; the 
