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Aug. F. Foerste 
in association with those having quadrate outlines, and both are 
connected by so many intermediate forms, that they are not 
distinguished here even as varieties. 
The muscular area of the pedicel valve equals about three- 
tenths of the width of this valve. Postero-laterally it is distinctly 
bounded by a sharp border extending forward from the teeth; 
laterally, this border rapidly diminishes in height; and along the 
anterior margin of the area there usually is no trace of the bor- 
der. A rather faint median line of elevation, widening poste- 
riorly, traverses this area and indicates the line of attachment of 
the adductor muscles. In the interior of the brachial valve, the 
two lobes of the cardinal process, the divergent crural plates, 
and the median ridge extending forward from the callosity imme- 
diately in front of the cardinal process, are well developed, con- 
sidering the size of the shell. The median ridge, mentioned above, 
terminates at the anterior end of the adductor areas. Sometimes 
the adductor areas are clearly defined anteriorly, but frequently 
there is only a rather vague suggestion of this outline. The 
vascular ridges and sinuses found along the median parts of the 
brachial valve in other species of Strophomena, usually are imper- 
fectly indicated or absent. The location of the radiating striae 
ornamenting the exterior of the shell frequently can be detected 
on the interior. Aside from the markings already described, the 
general surface of the interior is smooth, or is covered by minute 
papillae seen only under a magnifier. 
In Stony Hollow, northwest of Clarksville, in Clinton county, 
Ohio, Strophomena sulcata is seen at the very base of the Clarks- 
ville division of the Waynesville member, immediately above 
the Orthoceras fosteri clay bed. From this horizon, it ranges 
upward a distance of 7 feet, and is fairly common in several 
layers. Most of the specimens are distinctly sinuate anteriorly, 
as the name suggests, and the radiating plications of most speci- 
mens are rather coarse, a fact which is true also of the speci- 
mens found at the lower Hehertella insculpta horizon. Occa- 
sionally, however, specimens are found in which these plications 
are about as numerous as in the Liberty and Whitewater forms. 
About I foot above the base of the Clarksville division, in Stony 
Hollow, northwest of Clarksville, brachial valves of Strophomena 
sulcata occur, which are almost evenly convex. Some of these 
specimens are 24 mm. wide. In that case they bear some resem- 
