846 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
MURINELLA CANCELLATA Cooper, new species 
Plate 217, H, figures 20-22 
Shell large, with the widest part just anterior to the hinge, cardinal extremi- 
ties rounded, obtuse; lateral margins gently rounded, sloping to the middle; 
anterior margin broadly rounded. Surface marked by costellae of unequal size, 
separating areas of fine costellae; 3 or 4 of the larger costellae occupy a space 
of 5 mm. at the front and as many as Io of the finer costellae may occupy the 
spaces between the larger ones; all costellae are crossed by fine elevated lines, 
about 5 to a millimeter near the middle, which produce a cancellated effect. 
Pedicle valve fairly strongly convex, with the greatest curvature anterior to 
the middle; umbonal region convex and area anterior to umbo somewhat swol- 
len ; lateral and anterior slopes moderately steep ; valve not markedly geniculated 
but surface is bent toward the brachial valve about 13 mm. anterior to the beak. 
Palintrope short for such a large shell; interarea flat, approximately orthocline. 
Foramen small. 
Brachial valve with visceral area slightly convex for 10 mm. anterior to the 
beak where the valve is bent at an obtuse angle toward the brachial valve. Genicu- 
lated rim about 6 mm. long. Chilidium short, cardinal process large. 
Measurements in mm.—Holotype, length 18.8, brachial length 16.4, midwidth 
23.4, hinge width 22.6, thickness 5.4. 
Type.—Holotype: 117631. 
Horizon and locahity.—Benbolt formation in Virginia: West of Rye Cove, 
Clinchport (T.V.A. 188-NW) Quadrangle. 
Discussion.—This is a large species characterized by a fairly deeply concave 
brachial valve and beautifully cancellated shells. It is much larger than 
M. speciosa and differently ornamented. It is very suggestive of M. semureducta, 
but that species has a less deeply concave brachial valve and is proportionately a 
much wider species. This species differs from M. muralis and M. partita in the 
strongly concave brachial valve. 
MURINELLA MURALIS Cooper, new species 
Plate 226, D, figures 10-28 
Shell large, planoconvex in profile, semielliptical in outline; anterior com- 
missure rectimarginate ; lateral margins gently rounded ; widest part of shell just 
anterior to hinge; anterior margin broadly rounded. Surface marked by costellae 
of unequal size, 4 or 5 smaller costellae between the larger ones and all crossed 
by strong concentric lines. 
Pedicle valve strongly convex in lateral profile, with greatest convexity near the 
middle. Median region swollen and with moderately steep slopes to the anterior 
and lateral margins. Teeth moderately large with sockets parallel to the hinge; 
dental plates short and flaring, with small umbonal cavities separating them from 
the inner side of the valve. Muscle area i impressed, transversely elliptical 
to subcircular in outline. 
