170 PALEONTOLOGY OF THE EUREKA DISTRICT. 
Valves with small incurved beaks situated well towards the anterior 
end of the nearly straight cardinal line. 
Surface, as shown by the impression left in the cast, marked by con- 
centric lines of growth. 
Dimensions: height, 4°"; breadth, 6.5°"; convexity of right valve, 17". 
Four specimens of this species have been obtained, all in the form of 
casts. The transverse subquadrangular form serves to distinguish it from 
Modiomorpha alta of the Hamilton Group of New York, which is the most 
nearly allied species. Some specimens that are referred to M. alta are 
almost identical in form, but the typical forms differ materially, as may be 
-seen by comparing our figure with those given of the New York species 
(Pal. N. Y., vol. v, pt. 1, Plates and Explanations, pl. xxxvii). 
Formation and locality—lLower Devonian; Lone Mountain, 18 miles 
northwest of Eureka, Nevada. 
Modiomorpha oblonga, n. sp. 
Plate v, fig. 7. 
Shell transversely elliptical or elongate-ovate. General surface mod- 
erately convex, with a distinct, rounded umbonal ridge. 
Hinge-line shorter than the length of the shell and nearly straight. 
Beaks anterior, small, and incurved. Surface marked by concentric lines 
of growth. 
Dimensions: height, 2.75°"; breadth, 5.5°"; convexity of left valve, 
OSS. 
This species is more nearly related to Sanguinolites ? Sanduskyensis Meek 
(Pal. Ohio, vol 1, p. 209, pl. xviii, fig. 3), from the Helderberg Group of 
Ohio, than to any other species with which we are acquainted. It is less 
expanded posteriorly, and the anterior extremity is not as nasute. The 
generic reference is made on the general form, as the hinge characters are 
unknown. 
Formation and locality—Lower Devonian of Atrypa Peak, Eureka 
District, Nevada. 
