Strophomena and Other Fossils 
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extending forward from the thickened portion of the shell beneath 
the cardinal process. The interior of the brachial valve is marked 
by irregular, elongated papillae or short ridges, which become 
coarser toward the vascular markings and toward the posterior 
parts of the shell, but are finer toward the lateral and anterior 
margins. Their arrangement usually is very irregular. Simi- 
lar markings are found on the interior of the pedicel valve. They 
give a roughened or shagreen effect to the surface of the interior. 
The most characteristic features of the exterior of the shell are 
the high hinge- area; the usually conspicuous wrinkling of the 
posterior part of the shell, approximately perpendicular to the 
hinge-line ; the very fine radiating striae on the pedicel valve, and 
the much coarser striae on the brachial valve. In a shell 33 mm. 
wide, the height of the hinge-area of the pedicel valve may equal 
4 or 5 mm. at the beak. In some of the thicker specimens, the 
height of this hinge-area may be fully 1.7 mm. within 2 mm. of 
the lateral terminations of the area. The wrinkling of the pos- 
terior part of the valves, perpendicular to the hinge-area, extends 
only a short distance from the area near the beaks, the extent of 
the wrinkling increasing toward the postero-lateral angles of the 
valves, sometimes involving the shell to a distance of 5 or 6 mm. 
from the hinge-area. The number of radiating striae on the pedi- 
cel valve frequently equals 18 to 21 in a width of 5 mm., 25 mm. 
from the beak, but may be as low as 14 in the same width. Occa- 
sionally, every fourth one of these striae is slightly more promi- 
nent. Usually the radiating striae are crossed by a set of irregu- 
lar concentric wrinkles and fine striae, accompanied occasionally 
by somewhat squamose lines of growth, rather irregular at the 
edges; moreover, the radiating striae tend to change more or less 
in direction, especially toward the anterior and lateral margins 
of the valves. The result is a peculiar irregular appearance of 
the markings on the exterior of the pedicel valve which is very 
diagnostic of this species. The number of radiating striae on 
the brachial valve equals 8 to 10 in a width of 5 mm. at 25 mm. 
from the beak. Toward the beak, every second or fourth 
striation may be more prominent, but anteriorly the striae are 
more nearly of the same size, or alternate in part, the intermediate 
striae being comparatively inconspicuous. The two valves differ 
greatly in the coarseness of their striations. 
The shells may attain a width of 40 mm. The length of the 
