880 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
PLATYMENA ? BELLATULA Cooper, new species 
Plate 230, B, figures 11-13 
Shell of medium size, attaining a width of about 3 inch; subrectangular in out- 
line, with the length slightly less than the width; sides gently oblique; anterior 
margin broadly rounded ; hinge forming the greatest width; cardinal extremities 
acute ; surface marked by costellae unequal in size, about 3 or 4 to the millimeter 
at the front margin. 
Pedicle valve with lateral profile gently but unevenly convex, the most convex 
part located in the posterior third; anterior profile evenly and gently convex. 
Umbo narrowly convex and with short, steep umbonal slopes to the posterolateral 
areas, median region gently swollen ; anterior slope long and gentle ; lateral slopes 
gentle. Interarea moderately long, apsacline; foramen small. 
Brachial valve very gently concave to flat in both profiles; umbo concave; 
posterolateral areas gently and narrowly concave; rest of valve nearly flat. 
Measurements in mm.— 
Brachial Hinge . 
Length length Midwidth width Thickness Height 
FIGIOLyPe Mele wk see ..e. 16.1 7 19.6 20.5 28 2.8 
Paratype .tonaes eo: 17.6 16.4 21.4 21.5+ 2.6 2.9 
Types.—Holotype: 117758; unfigured paratype: 117757. 
Horizon and locality.— Bromide formation (Pooleville member) in Oklahoma: 
On Spring Creek, sec. 17, T. 2 S., R. 1 W., Murray County; 162 feet below 
the massive limestone, second dam on Spring Creek, northwest of Woodford, 
Murray County. 
Discussion.—The interior of this species is unknown ; consequently it is placed 
in Platymena with a query. The species is about the same size as P. plana but 
the sides are more oblique, the shell thickness is greater, and the interarea is 
longer and has a prominent pseudodeltidium. 
PLATYMENA PLANA Cooper, new species 
Plate 230, A, figures 1-10; plate 266, D, figures 10-16 
Shell small, planoconvex in lateral profile; slightly wider than long. Hinge 
forming the widest part; cardinal extremities slightly alate. Lateral margins 
nearly straight to slightly oblique. Anterior margin narrowly rounded. Orna- 
mentation consisting of costellae of unequal size, the larger ones separated by I 
or 2 fine costellae and all crossed by fine threadlike concentric lines. At the front 
margin of a brachial valve 10 mm. in length 3 of the larger costellae occupy a 
space of I mm. 
Pedicle valve very slightly convex in lateral profile with the most convexity 
in the posterior third and the front somewhat flattened. Umbo narrowly con- 
vex and produced forward for about one-third the length as a low, narrow fold. 
Front half and anterolateral portions flattened. Slopes from umbo to cardinal 
extremities gentle. Interarea moderately long; pseudodeltidium short. 
Brachial valve characterized by a narrow, fairly deep sulcus originating at 
