Strophomena and Other Fossils 
111 
spicuous radiating vascular markings. The muscular area is 
large, compared with the size of the valves, but the postero- 
lateral border of this area does not join the hinge area farther 
exterior to the teeth than in many a specimen of typical Stropho- 
mena neglecta from Ohio and Indiana. One brachial valve is 
flattened for 20 mm. posteriorly, and then is strongly deflected 
downward at about 80 degrees for a distance of 30 mm., the 
direct length of the shell being 40 mm. Evidently, strong curva- 
tures are to be expected in some of the shells, anterior to the 
flattened posterior area, in Strophojnena planodorsata. The radi- 
ating striae were subequal or alternated in size, about 7 or 8 
oc curing in a width of 2 mm. On a brachial valve from the 
same locality, belonging to the Schuchert collection, there are 15 
subequal radiating striae in a width of 5 mm. near the anterior 
margin. Over the flattened area near the middle of the valve, 
some of the striae are more prominent, and are separated by 3 
to 5 finer ones. 
Two specimens of smaller size, from the Richmond beds of 
Wilmington, Illinois, also belonging to the Schuchert collection, 
are illustrated by Figs. 7 A, B, on plate VII, and Figs. 8 A, B, 
and Fig. 9 on plate IX of this Bulletin. On the flattened area 
of the brachial valve certain striae are slightly more promi- 
nent, and are separated from each other by 4 or 5 finer striae. 
Anterior to the flattened area, the striae become more nearly 
equal in size, about 19 or 20 occupying a width of 5 mm. along the 
anterior margin. The pedicel valve has a circular muscular 
area with flabellate markings. The margin of this area is 
scarcely raised above the general surface of the body cavity. 
At the hinge-line the area is better defined, but here the border 
does not meet the hinge-line distinctly exterior to the teeth. 
Possibly this border moves outward with increased maturity of 
the shell. The greatest convexity of the complete but somewhat 
crushed shell, 16 mm. from the hinge-line, is 10 mm. Height of 
the hinge-area of the pedicel valve, 4 mm. The shell is 26.5 mm. 
long, and the flattening of the brachial valve extends for a dis- 
tance of about 15 mm. from the beak. 
With these smaller forms of Strophomena planodorsata from 
Wilmington, Illinois, I have identified some specimens from the 
Richmond beds in western Tennessee. About 17 radiating, sub- 
equal striae occupy a width of 5 mm. Specimens with the flat- 
