806 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
where the valve is somewhat geniculated and the posterior half flattened. An- 
terior profile a very gentle bow with the highest part in the middle. Posterior 
margin nearly straight. Beak and umbo swollen and standing above the posterior 
margin and with the beak protruding slightly beyond the posterior margin. Cen- 
tral part slightly swollen and more prominent than the flanks which extend by 
a gentle slope to the cardinal extremities. Anterior and lateral slopes steep. 
Brachial valve with moderately concave umbonal region but strongly concave 
in the median part. Flanks bounding deepest part somewhat flattened. Cardi- 
nal extremities deflected toward the pedicle valve. Interarea anacline. 
Measurements in mm— 
Hinge 
Length Width width Thickness 
PAGCOR vs hoe ra tolta ns 'siaSice lends Bete 4.3 9.6 11.5 ? 
Paratype (IIOD2ZOD) 22... ias6.s 8 ate ors 5% 3.8 7.3 0.7 ? 
~ (F809280C)% tay chyna l ee ete 4.2 8.0 8.9 ? 
Types.—Holotype: 110929a; figured paratypes: 110924, 11092Qb-d. 
Horizon and locality—Whitesburg formation in Tennessee: 14 miles west of 
Bulls Gap, Bulls Gap (T.V.A. 171-SE) Quadrangle. 
Chatham Hill formation in Virginia: On the Grayson Farm, 4 miles south- 
west of Bland, Bland County. 
Discussion—Compared to A. tricostellata, this species is much larger, more 
convex, and has more numerous large costellae. 
ANISOPLEURELLA TRICOSTELLATA Cooper, new species 
Plate 193, A, figures 1-4; plate 195, A, figures 1-5 
Shell small, about twice as long as wide at the hinge; cardinal extremities 
acutely angular ; lateral margins slightly convex, front margin broadly rounded. 
Surface marked by costellae of unequal size ; 3 costellae stronger than the others 
divide the shell into 4 parts; 1 costella originates at the umbo and extends to 
the anterior margin, the other 2 extend to the anterolateral margins. The sur- 
face between the stronger costellae are marked by very fine, crowded costellae of 
unequal size and numbering about 12 or 13 in I mm. at the front margin. Cos- 
tellae cancellated by fine concentric fila. Flanks marked by interrupted concen- 
tric undulations. 
Pedicle valve moderately convex, with the greatest convexity at about the 
middle; beak protruding very slightly beyond posterior margin; umbo swollen ; 
portion of shell occupied by 2 medial quadrants as marked off by strong radii 
inflated ; outer flanks flattened; posterior margin defined by a thickened rib or 
costella diminishing in size toward the beak. 
Brachial valve gently concave with the maximum depression at the middle; 
flanks and cardinal extremities somewhat flattened. Adductor field forming 2 
well-rounded and large lobes, each lobe divided by an oblique ridge; median 
septum short and slender. Cardinalia as in Sowerbyella. 
