952 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
thirds the width; sides gently rounded to nearly straight; cardinal extremities 
obtuse, narrowly rounded; anterior margin strongly rounded; anterior com- 
missure narrowly sulcate. Costellae numbering 2 or 3 to the millimeter at the 
front margin. 
Pedicle valve deeper than the brachial valve, gently convex in lateral profile 
with the maximum convexity at the umbo; anterior profile forming a broad tri- 
angle, the median region carinate and the sides sloping moderately. Beak low, 
incurved; umbo carinate, the carina continuing from the beak to beyond the 
middle and becoming more rounded in the anterior third, thus forming a fold 
from beak to margin. Median region inflated. Interarea moderately long, curved, 
apsacline. 
Brachial valve gently convex in lateral profile and with the anterior third 
somewhat flattened ; anterior profile bilobed, with 2 convex lobes with a shallow 
depression occupying the middle between them. Umbo deeply sulcate; sulcus 
narrow, extending to the anterior margin and becoming wider and shallower in 
its passage to the front margin. Flanks bounding sulcus moderately inflated ; 
lateral slopes short and gentle. 
Pedicle interior with small teeth, flaring dental plates with a thickening an- 
terior to them and enclosing the sides of the muscle area ; diductor scars elongate, 
separated anteriorly; adductor field narrowly elliptical. Brachial interior with 
brachiophores united to median septum; cardinal process with moderately long, 
cleft shaft and small myophore. 
Measurements in mm.— 
Brachial Hinge 
Length length Width width Thickness 
RTOS T Sicmiies) SAU Perey 11.4 10.7 13.2 9.9 4.9 
Paratype. (117365b) ss. «2 «62% 12.8 12.4 15.7 10.2 5.4 
< CT P7SGEE) oA susie oftincs rf fer) II.1 13.9 9.3 5.0 
Types.—Holotype: 117365a; figured paratypes: 117365b,e,f,h,i, 123239a; un- 
figured paratypes: 117365¢,d,¢. 
Horizon and locality—Hermitage formation (base) in Tennessee: On U. S. 
Highway 70S-41 near its junction with Spence Lane, 4.2 miles southeast of 
Nashville, Hermitage (15’) Quadrangle. 
Discussion.—This is a large species characterized by robust form, subrectan- 
gular, fine costellae and deep sulcus and corresponding subcarinate fold on the 
pedicle valve. It is the largest species of Dalmanella described herein and differs 
from all others in this monograph in that respect. It differs from D. crassicos- 
tellata also in having finer costellae, deeper sulcus, and stronger fold. 
Some of the specimens are characterized by nearly right angled cardinal ex- 
tremities, but in others the cardinal extremities are strongly rounded. In other 
respects these specimens are like the more typical square-shouldered forms. The 
ones with rounded cardinal extremities may ultimately prove to be related to 
Onniella rather than Dalmanella, but this could not be demonstrated with the 
collections available. 
