48 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 134 
Pedicle valve moderately convex in lateral profile and with the 
greatest convexity located in the umbonal region; beak strongly in- 
curved; umbonal region narrowly swollen and marked off from main 
body of valve by steep slopes; sulcus shallow, equal in width to about 
one-quarter the valve width or less, originating about 4 mm. anterior 
to the curved umbo; areas bounding sulcus moderately swollen; 
slopes to margins steepening posteriorly and steepest along the umbo ; 
cardinal extremities flattened. 
Brachial valve nearly flat in profile, but strongly geniculated around 
the margin; point of geniculation 15 mm. anterior to beak; umbonal 
region concave; fold low, widening anteriorly and originating about 
5 mm. anterior to the beak. Grooves bounding sulcus shallow, deepest 
near the middle; flanks slightly swollen. 
Measurements in mm.—Holotype (pedicle valve), length 17.6, 
width (based on half measure) 24, height 6.5; paratype, U.S.N.M. 
125462a (brachial valve), length 16.1, hinge width 17.1; midwidth 
23.6. 
Types.—Holotype, U.S.N.M. 125353; figured paratypes, U.S.N.M. 
125352a, 125354; unfigured paratypes, U.S.N.M. 125352b, 125462a,b. 
Localities —636; F; P12; S46, S103; U.O. 2205-1. 
Discussion.—This species is characterized by its small size, the 
geniculated anterior margin of the brachial valve and the very fine 
spines. The largest specimen from Oregon is about the same size as 
the type specimen of W. montpelierensis figured by Girty (1910), 
but the Oregon species is more deeply sulcate on the pedicle valve 
and has a somewhat more prominently folded brachial valve and 
finer spines. Girty’s illustrations do not indicate the strong genicula- 
tion of the anterior margin of W. montpelierensis that is such a 
prominent character of the Oregon species. If this were present in the 
Idaho form, a fairly deep trough would appear parallel to the margin. 
ECHINOCONCHUS INEXPECTATUS Cooper, new species 
Plate 8C, figures 13-26 
Shell small to medium size for the genus, somewhat trapezoidal to 
pentagonal in outline; sides broadly rounded; greatest width located 
at about two-thirds the length from the umbo. Hinge narrower than 
the shell at its widest part, equal to about two-thirds the width. 
Anterolateral extremities narrowly rounded; front margin gently 
rounded. Surface of both valves marked by conspicuous concentric 
growth lamellae bearing rows of spines of more than one size. 
Pedicle valve strongly convex in lateral profile with the beak and 
umbo curved over the hinge line; beak curved over and pointing at 
