328 . SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
TAPHRORTHIS PECULIARIS Cooper, new species 
Plate 38, C, figures 16-20; plate 30, A, figures 1-6; plate 108, B, figures 6-14; 
plate 108, D, figures 19, 20 
Of moderate size for the genus, wider than long and with the hinge narrower 
than the greatest shell width which is located at about the middle. Cardinal ex- 
tremities obtusely angular. Sides gently rounded; anterior margin truncated. 
Surface multicostellate with 4 generations of intercalated costellae besides the 
primary set. Strong concentric elevated lines cross the costellae and interspaces. 
Twelve costellae of all sizes appear in a space of 5 mm. at the front of a valve 
Ir mm. long. 
Pedicle valve moderately convex in lateral profile and strongly convex in an- 
terior profile. Beak erect and with prominent swollen umbonal region. Median 
portion of valve full and with a moderately steep anterior slope. Lateral slopes 
steep. Interarea long, curved, apsacline to orthocline; delthyrium open or par- 
tially restricted by narrow lateral plates. Pedicle interior with small teeth hav- 
ing moderately deep fossettes. Dental plates short, the umbonal cavities partially 
filled by callus material. Muscle area typically orthoid with a cordate outline hav- 
ing large diductor impressions and an elongate adductor field often slightly raised 
anteriorly and producing an incipient pseudospondylium. 
Brachial valve gently convex in lateral profile but broadly arched and depressed 
medially in anterior profile. Beak small, protruding slightly posterior to the 
posterior margin. Umbo sulcate, the sulcus produced anteriorly to the front 
margin, widening in this direction but becoming shallower. Flanks bounding 
sulcus gently swollen and with gentle anterolateral slopes but steeper slopes to 
the cardinal extremities. Interior of brachial valve with a short median ridge 
not reaching to the middle of the valve; notothyrial platform moderately thick 
and united with the median ridge. Notothyrial cavity shallow ; cardinal process 
a low, simple septum. Brachiophores short, slender and defining small, shallow 
sockets. Adductor field small. 
Measurements in mm.— 
Length Width Thickness 
Holotype (pedicle valve) yee. 22 ste cjccte te ome 9.9 12.8 a7 
Paratype (brachial valve 109883b).......... II.1 14.5 2.4 
Types.—Holotype: 109883¢; figured paratypes: 109883b,e, 116892, 116893a,b, 
117984a,b,e; unfigured paratypes: 109883a,d,f-j, 117984c,d. 
Horizon and locality —Effna-Rich Valley formations in Virginia: At Porter- 
field Quarry, 5 miles east of Saltville, Maccrady (T.V.A. 218-NW) Quadrangle. 
Botetourt formation in Virginia: Opposite the road intersection with Hays 
Creek, 2 miles northwest of Brownsburg, Lexington (15’) Quadrangle; north 
of Virginia Highway 114, 2.3 miles west of Montgomery-Roanoke County line, 
about 12 miles northeast of Blacksburg, Montgomery County. 
Pratt Ferry formation (lower third) in Alabama: 0.2 mile southeast of Pratt 
Ferry, Blocton (15’) Quadrangle. 
