222 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
PALAEOGLOSSA sp. 1 
Plate 10, C, figures 14-17 
This is a large form, nearly twice as long as wide, with gently rounded sides 
and broadly rounded anterior margin. Valves subequally convex. Pedicle valve 
with apical angle of 95°. Brachial valve with broadly rounded posterior. Brachial 
valve with long median ridge. 
Measurements in mm.—116775, length 19.5, width 11.5, thickness 4.2. 
Figured specimen.—116775. 
Horizon and locality—Edinburg formation (Cyrtonotella zone) in Virginia: 
100 yards west of U. S. Highway 11, 1 mile northeast of Strasburg, Strasburg 
(15’) Quadrangle. 
PLECTOGLOSSA Cooper, new genus 
(Greek plektos, fold; glossa, tongue) 
Oval in outline and lenticular in profile; brachial valve slightly deeper than 
the pedicle valve. Pedicle beak acute. Surface marked by regular, elevated con- 
centric lines. 
Pedicle beak with a depressed pedicle plate marked medially by a low fold. 
Posterior margin of brachial valve thickened as in Pachyglossa. 
Genotype.—Plectoglossa oklahomensis Cooper, new species. 
Discussion.—This genus is characterized by its oval outline and compressed 
lenticular profile with regular, elevated concentric ridges. The interior of the 
posterior margin of the brachial valve is like that of Pachyglossa, but the apical 
features of the pedicle valve are unlike any other linguloid described herein in 
having a concave apical plate marked medially by a low fold. The exterior form 
and ornamentation of this genus suggest Trigonoglossa, but that genus differs 
in having a more triangular outline, more compressed valves, and a different 
type of pedicle plate. In Trigonoglossa this plate is deeply concave and lies close 
to the floor of the valve. Furthermore, the sides are not marked by a ridge and 
are much more narrowly folded. 
PLECTOGLOSSA OKLAHOMENSIS Cooper, new species 
Plate 6, C, figures 7-15 
Shell small, grayish blue to black in color, oval in outline. Posterolateral mar- 
gins straight, forming indistinct shoulders where they join the lateral margins at 
about one-third the length from the beak. Greatest width at about the middle. 
Lateral margins gently rounded; anterior margin strongly rounded. Surface 
marked by distant, fairly evenly spaced raised concentric lines between which 
occur irregular fine concentric lines. Young portions of valves at umbones dark 
and smooth, marked only by fine concentric lines. 
Pedicle valve with narrow beak; lateral profile moderately convex with the 
greatest convexity near the middle; anterior slope long and gentle; anterior 
profile fairly strongly convex and somewhat swollen medianly; lateral slopes 
