98 
Aug. F. Foerste 
and close of the Blanchester division, during the ingression of 
Hehertella insculpta; also early in the Liberty, during the ingres- 
sion of Dinorthis subquadrata; probably also during the middle 
of the Blanchester, during the ingression of Strophomena neglecta, 
and later, during the ingression of Austinella scofieldi. During 
the greater part of the Liberty, however, and during all of the 
Whitewater, this basin in Ohio and Indiana appears to have been 
entirely cut off from the Mississippi Valley Bichmond seas. 
Strophomena vetusta, James 
{Plate VI, Figs. 2 A, B, C, D, E, F, G, H) 
The muscular area of the pedicel valve equals in width about 
one-third to two-fifths of the width of the shell. Postero-later- 
ally, the muscular area is abruptly limited by a sharply ascending 
border. Antero-laterally, the surface of the area rises more 
gradually toward the border, and here the limiting border may 
rise sharply above the general surface of the interior of the valve, 
or only the outer slope of the border may be sharply defined. 
The surface of the muscular area is not conspicuously striated 
in a radiate or flabellate manner, as in Strophomena neglecta. 
Anteriorly, the lateral border is deflected forward, leaving a 
rather broad median gap, which is one of the characteristics of 
this species. A rather narrow median ridge, widening only 
slightly posteriorly, indicates the line of attachment of the adduc- 
tor muscles. The deflected anterior terminations of the lateral 
borders of the muscular area are extended anteriorly as ridges, 
between which one or two additional ridges may appear, the 
various ridges being separated by the vascular sinuses. These 
ridges and intermediate grooves are much less distinct than those 
on the median parts of the brachial valve, and usually extend only 
about half way from the muscular area toward the anterior mar- 
gin of the valve. The shell usually is only moderately thickened 
along the anterior and lateral edges. 
The interior of the brachial valve is marked by four strong 
parallel ridges with the intermediate vascular sinuses. Posteri- 
orly, they terminate within the diductor area, the two inner 
ridges having a tendency to unite with the median elevation 
Cincinnati Quarterly J our 7ial of Science, vol. i, p. 241, 1874. 
