78 
A ug. F. Foerste 
hinge line beyond the general width of the shell can not be verified. 
The fasciation, however, is distinct, especially on the pedicel 
valve. About lo striations begin at or very near to the beak, and 
between these an approximately equal number is intercalated 
almost immediately, so that about i8 fairly prominent striae extend 
from near the beak to the margins of the shell. These striae have 
a tendency to occur in pairs, as though resulting from the division 
of the more primary striae. About 7 mm. from the beak other 
striae are intercalated, and anterior to this there may be a few 
additional striae, so that the anterior and lateral parts of the shell 
are marked apparently by fascicles of striae, the fascicles consisting 
of three or four striae near the median parts of the shell, the pri- 
mary striation of each fascicle being considerably more conspicu- 
ous, as in Plectorthis fs si costa. The fascicles have a tendency to 
occur in pairs. 
Length of shell, 15 mm.; width across the middle, 19 mm.; depth 
of the entire shell, 6 mm. The valves are nearly subequal in con- 
vexity. 
Osgood bed: New Marion, Indiana. 
Hebertella (Schizonema) nisis, Hall. | 
This species is evidently closely related to Hehertella fissi plica, j| 
it shows about the same range of variation in the coarseness and 
frequency of the radiating stride and in the curvature from front j! 
to rear of the pedicel valve. It has the median depression of the jl 
brachial valve; the high cardinal area, inclined strongly backward, 
of the pedicel valve; the pedicel valve is conspicuously more con- |l 
vex and deeper than the brachial valve; the delthyrium is narrow. | 
It differs from Hehertella fissipUca in the greater convexity of [ 
the brachial valve and the greater height of the cardinal area of | 
the pedicel valve. This area is more incurved near the beak in 
one of the specimens figured by Hall than in any specimens of | 
Hehertella fissiplica so far seen. See figs. 4 to 8 on plate 9 of the 
Twenty-seventh Report on the New York State Cabinet. 
Louisville bed : in the upper strata exposed in the quarries along 
Beargrass creek east of Louisville, Kentucky. 
