34 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 134 
marked anteriorly to the beak by a shallow sulcus. The brachial valve 
shares the curvature of the pedicle valve, thus producing a shell with 
only a thin body cavity. The spines of the pedicle valve are short 
and have a crude quincuncial arrangement. The brachial valve im- 
pression is pitted, each pit corresponding to a spine on the pedicle 
valve. A typical specimen (hypotype, U.S.N.M. 124021) is 28 mm. 
long, 41 mm. wide, and 4 mm. thick at the umbo. The height from 
the margins to the point of greatest curvature is about 12 mm. The 
specimen figured by Tschernyschew (1902, pl. 30, figs. 2a-c), has 
almost the same measurements as the figured Oregon specimen. 
Types.—Figured hypotype, U.S.N.M. 124021. 
Localities.—638; L8; P1o; S4o, S41, S43, S46, S56, S70, S87, 
S103; U.O. 2201-1, 2204-3. 
ANTIQUATONIA RETICULATA Cooper, new species 
Plate 3A, figures 1-9 
Large, subquadrate in outline but with the width slightly greater 
than the length; margins not clearly preserved ; somewhat more than 
posterior half finely reticulate; trail costellate, costellae unequal in 
size, narrowly rounded and separated by spaces about equal in width 
to the width of the costellae; costellae numbering about 4 in 5 mm. 
at the anterior part of the trail. 
Pedicle valve unevenly convex in lateral profile, the anterior third, 
except for the beak and umbo, gently convex; median third narrowly 
convex and anterior third or trail gently convex. Beak strongly in- 
curved but not protruding beyond the hinge line. Umbo broadly 
swollen and with steep lateral slopes. Sulcus originating about 10 
mm. anterior to the beak, shallow at its origin but becoming deeper 
anteriorly where it forms a deep, broadly V-shaped trench in the 
trail. Flanks bounding sulcus in the visceral region moderately swol- 
len but on the trail they are strongly swollen and have steep, rounded 
lateral slopes. 
Brachial valve gently concave in lateral profile but with a short 
trail geniculated at about a right angle to the visceral region. Umbo 
moderately deeply sulcate. Median fold low, fairly broad but be- 
coming nearly obsolete on the trail. 
Measurements in mm.—Holotype, length 44.0, width at middle 
50.4+, surface length 90, height 33.5?; brachial valve, paratype, 
U.S.N.M. 125349, length 36.3, width 48.1, surface length 52. 
Types.—Holotype, U.S.N.M. 125348; figured paratypes, U.S.N.M. 
125347, 125349. 
