FOSSILS OF THE DEVONIAN, 169 
As far as can be determined by a comparison of the single right valve 
that we have of this species with specimens, and also Professor Hall’s figures, 
it is identical with the New York species. It occurs in association with the 
following Chemung species: Orthis.impressa, Productus speciosus, P. lachry- 
mosa, vars. lima and stigmata, Spirifera disjuncta, Athyris Angelica, Rhyncho- 
nella sinuata, Sanguinolites rigidus. 
Formation and locality—Upper Devonian, at The Gate, northwest of 
Eureka, Nevada. 
Subgenus PLETHOMYTILUS Hall. 
Mytilarca (Plethomytilus) oviformis Conrad. 
Plate vy, fig. 11. 
Inoceramus oviformis Conrad, 1842. Jour. Acad. Nat. Sci., Philad., vol. viii, p. 246, 
pl. xiii, fig. 7. : 
Mytilarca oviformis Hall, 1870, Prelim. Notice Lam. Shells, p, 21. 
Plethomytilus oviformis Hall, 1883. Pal. N. Y., vol. v, pt. 1; Plates and Explanations, 
p. 11; pl. xxxi, figs. 1-8. 
Mytilarca (Plethomytilus) oviformis Hall, 1884. Pal. N. Y., vol. v, pt. 1, p. 255; pl. 
Ixxxvii, fig. 8. 
But a single left valve of this species has been obtained. In form and 
external characters it corresponds too closely with M. (P.) oviformis of the 
Hamilton Group of New York to admit of a specific separation. It may be 
that if the ligamental area and hinge were known, differences of generic 
value would appear, but with the present knowledge of the shell this is not 
anticipated. 
Formation and locality—lLower Devonian, Lone Mountain, 18 miles 
northwest of Eureka, Nevada. 
Genus MODIOMORPHA Hall. 
Modiomorpha altiforme, n. sp. 
Plate v, fig. 9. 
Shell transverse, suboval to subquadrangular in outline. General sur-_ 
face strongly convex, with the umbonal ridge prominent. 
