20 PALEONTOLOGY OF THE EUREKA DISTRICT. 
Kutorgina sculptilis Meek (Sp). 
Plate i, figs. 7, 7a, b; pl. ix, fig. 7. 
Iphidea (? ?) sculptilis Meek, 1873. Sixth Ann. Rep. U.S. Geol. Surv. Terr. for the year 
1872, p. 479. | 
Kutorgina minutissima Hall & Whitfield, 1877. U.S. Geol. Expl. Fortieth Par., 
vol. iv, p. 207, pl. i, figs. 11, 12. 
Shell minute, semicircular to subquadrangular; hinge line usually a | 
little shorter than the greatest width of the shell; sides slightly rounded; 
antero-lateral angles rounded; frontal margin gently convex or nearly 
straight along the middle. _ 
Ventral valve obliquely depressed, subconical, with the somewhat ob- 
tusely pointed apex on, or slightly extending over, the cardinal line; area 
vertical or bending a little backward, triangular; width a little more than 
twice the height, but not as broad as the shell, owing to the sides of the latter 
curving in to meet the straight area at an angle of about 50°; foramen (?) 
large, dorsal valve depressed convex, most elevated on the umbo; beak a- 
little depressed, scarcely projecting beyond the cardinal line; mesial sinus 
faintly defined, not much more than a slight flattening in many examples; 
area low, general characters unknown. 
Surface of the shell marked by very fine, sharp, elevated, concentric 
lines, that coalesce or bifurcate irregularly, giving a peculiar, interrupted, 
wavy appearance under the magnifiér; these lines extend around on the 
sides of the posterior side or area to the edges of the triangular foraminal- 
like opening. Slightly irregular, slender, depressed or elevated interrupted 
lines radiate from the beak or apex; they vary in strength and number, and 
on some shells are scarcely discernible, although forming a prominent feature 
in many individuals. 
Length of largest shell observed, 2.5"; breadth, lps depth of ven- 
tral valve, 1.25"; of dorsal valve, 0.5™™. 
The type of Iphidea (??) sculptilis (Meek) is a strongly marked ventral 
valve of this species from the east side of the Gallatin River, Montana, where 
it is associated with Acrotreta gemma Billings, and Ptychoparia Oweni Meek. 
