Strophomena and Other' Fossils 
93 
usually extending forward from the muscular area toward the 
anterior margin of the shell, are either absent or relatively indis- 
tinct. The cardinal process is prominent, extending at right 
angles from the flattened area anterior to the beak. It is bi-lobed, 
and each lobe is grooved along the top, the grooves making angles 
of about 45 degrees with each other. 
At the time the original description was published, nothing 
was known of the interior of the shell, and hence its description 
was based upon the appearance of the exterior. One of the chief 
characteristics of this part of the shell consists in the fineness 
and comparative equality in size of the radiating striae. At a 
distance of 30 mm. from the beak, the number of these striae 
varies from 12 to 15 in a width of 5 mm. Fifty millimeters from 
the beak, their number may equal only 8 or 9 in a width of 5 mm. 
The radiating striae on the pedicel valve are distinctly finer, 
compared with the more prominent striae on the brachial valve; 
in one case there were 15 striae in a width of 5 mm. while on the 
brachial valve there were 12 in the same width. Occasionally, the 
striae are distant from each other, and only 9 or 10 may be found 
in a width of 5 mm. at a distance of 30 mm. from the beak along 
the median part of the brachial valve. The radiating striae are 
crossed by much finer concentric striae, which usually are very 
distinct, under a magnifier, especially on the brachial valve. 
Compared with other species at the same horizon, the shell of 
Strophomena neglecta is large and thin. Specimens 50 mm. in 
width, 40 mm. in length, and 15 mm. in convexity occur, but 
specimens 45 mm. in width, 35 mm. in length, and 12 mm. in 
convexity are more common. The flattened area anterior to the 
beak of the brachial valve extends for a distance of about 15 mm. 
from the hinge-area. The larger shells appear rather strongly 
and evenly convex when viewed from the side, the maximum 
curvature being about 20 mm. from the beak. 
Compared with Strophomena vetusta, the hinge-area of the pedi- 
cel valve of Strophomena neglecta is more narrow; the brachial 
valve is more convex, and hence more deflected anterior to the 
postero-lateral angles; the flattened area of the brachial valve 
extends farther from the beak ; the convexity anterior to the beak 
of the pedicel valve is more prominent and extends farther from 
the beak; the radiating striae of the brachial valve are finer; the 
vascular ridges and sinuses of the median parts of the brachial 
