452 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
ately broad and gently sloping to the margins. Cardinal process thick and bulb- 
ous ; brachiophore plates short and stout. 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
Holotype .shersisvhiiaitecs. 16.9 15.5 20.3 14.7 9.9 
Paratype. (8 17O22D)) | ssa) o sts ee 20.4 19.0 24.4 17.9 12 
Types.—Holotype: 117022a; figured paratypes: 110837a-d, 117022b; un- 
figured paratype: 110837e. 
Horizon and locality—Basal Martinsburg formation (basal part with Brongni- 
artella referable to the Salona formation) in Virginia: On Virginia County 
Highway 617=0910, 0.15 miles north of Green Mount Church, Broadway (15’) 
Quadrangle. 
Discussion.—This species can be readily recognized by its large size and coarse 
costae. It is unlike any other species described in this monograph except P. obesa. 
That species, however, is a much deeper one which, as far as known, does not 
attain the large size of P. ponderosa. 
PLECTORTHIS PUNCTATA Cooper, new species 
Plate 84, D, figures 19-23; plate 84, F, figures 33-35 
Shell small for the genus, wider than long; hinge narrow; valves subequally 
convex, the pedicle valve having the greater depth; anterior commissure broadly 
unisulcate ; sides rounded ; anterior margin somewhat truncated. Surface marked 
by 31 costae at the front margin; some costae on the flanks bifurcating or inter- 
calated. Costae bearing 2 rows of prominent pits. 
Pedicle valve moderately convex in both profiles; median region swollen; lat- 
eral slopes long and moderately steep. Brachial valve gently convex in lateral 
profile ; broadly convex in anterior profile; sulcus originating at the umbo, widen- 
ing anteriorly, prominent in the young, becoming shallow anteriorly and disap- 
pearing in adults. Lateral regions swollen. 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
TIOIGEV DE) 6c sss sins tunes seaphebes ? 8.1 11.0 7.8? 1.8? 
| tg) Gk 3”) a ge a 6.0+ 6.4 8.5 6.2 aah 
Types—Holotype: 110836a; figured paratypes: 117023b, 117024; unfigured 
paratypes: 110836b, 117023a. 
Horizon and locality —Tulip Creek formation in Oklahoma: On West Spring 
Creek, NW} sec. 6, T. 2 S., R. 1 W.; NE corner sec. 1, T. 2 S., R. 2 W., 24 
miles east of Pooleville, Murray County; first creek east of U. S. Highway 77, 
SEXNELNE} sec. 25, T. 2 S., R. 1 E., Carter County. . 
Discussion.—This species is similar to P. symmetrica in size and general form 
but differs in having a more strongly convex brachial valve characterized by 2 
rows of pits on each side of the costae. 
