Strophomena and Other Fossils 73 
Strophomena planumbona, HalP 
{Plate VIII, Figs. 1 A, B, C, D, E; Plate IX, Figs. S A, B; Plate IV, Figs. 1, 
3, 4; Figs. 3 A, B, are typical) 
The types of Strophomena planumbona, numbered 918-3, are 
preserved in the American Museum of Natural History in New 
York City. They are labelled as coming from Cincinnati, Ohio, 
but the species occurs only at horizons belonging stratigraphi- 
cally above the highest beds exposed at Cincinnati. In the 
original description the localities mentioned are Cincinnati and 
Oxford (Ohio), Madison (Indiana), and Maysville (Kentucky). 
The species does not occur at Cincinnati, although specimens have 
been sent out by Cincinnati collectors to many museums in this 
country and in Europe. The specimens found at Maysville, 
Kentucky, here are described as Strophomena concordensis. 
At Oxford, Ohio, and Madison, Indiana, Strophomena planum- 
bona is common in the Clarksville and Blanchester divisions of 
the Waynesville bed. Lithologically, the types closely resemble 
specimens of this species collected at Madison, Indiana, but their 
exact origin is unknown. Undoubtedly they were obtained from 
the Waynesville bed. 
Fig. 4 a, on plate 31 B, New York Paleontology , vol. I, repre- 
sents the pedicel valve. The specimen is entire, presenting both 
valves. The chief feature of the pedicel valve is the presence 
of distinctly stronger striae, separated by much finer striae, 
usually three in number. Anterior to the middle of the shell, 
the middle one of the group of finer striae frequently becomes 
more conspicuous, and additional finer striae come in, preserving 
the appearance of stronger striae, each pair being separated by 
several finer striae. The tendency toward the alternation of 
single stronger striae with two or three distinctly finer striae is 
shown also by the brachial valve, especially along the lateral 
margins, and over the flattened portions of the valve as far ante- 
rior to the hinge-line as the area where the more rapid downward 
curvature of the shell begins. Along the anterior parts of the 
brachial valve, there is a tendency toward an alternation between 
single stronger and single finer striae. In slightly weathered 
specimens, in which the intermediate finer striae are not readily 
^ New York Paleontology, vol. i, p. 112, 1847. 
