40 
Aug. F. Foerste 
area, and serves as a line of attachment for the adductor muscles. 
Occasionally a parallel ridge traverses this area, on each side of 
the median one. These lateral ridges correspond to the posterior 
terminations of the two inner vascular ridges of other species of 
Strophomena. The remainder of the inner surface of the pedicel 
valve, outside of the muscular area, appears radiately striated, 
owing to the thinness of the shell permitting the striation of the 
exterior surface to be seen. 
The lobes of the cardinal process of the brachial valve are nar- 
row and small. The extremities of the crural plates frequently 
deviate but little from the hinge-line. The adductor scars are 
not well defined laterally or anteriorly. The median ridge extend- 
ing forward from the cardinal process frequently is bi-lobed at a 
point almost on a line with the region where the margin of the 
adductor scars should be. A parallel ridge occasionally is found 
on each side of this median one. The remainder of the interior 
is radiately striated on account of the thinness of the shell. 
Radiating striae crossing the exterior surface rather angular, 
subequal, from 10 to 12 in a width of 5 mm. near the anterior 
margin of the shell. 
Owing to the thinness of the shell, it occurs usually in a frag- 
mentary condition. The fragments rarely are preserved by col- 
lectors. The most satisfactory specimens consist of single valves 
adhering by one of their surfaces to the rock. The vertical range 
of Strophomena hallie needs further study. It probably extends 
throughout the Eden, but the species is common only at cer- 
tain horizons in the middle or Southgate division of the Eden. 
Strophomena hallie was described from 150 feet above the Ohio 
River, at Cincinnati, Ohio, from strata evidently belonging near 
the center of the middle or Southgate member of the Eden, but 
it is listed by Nickles also from the lower or Economy member. 
West of Foster, in the northwestern corner of Bracken county, 
and also opposite Utopia, several miles east of Wellsburg, in 
Kentucky, Strophomena hallie occurs along the railroad at the 
level of the lower Eden, but it may have slipped down the hill. 
Along the railroad, southeast of Maysville, Kentucky, the fol- 
lowing section is exposed: 
