22 
BULLETIN OF THE LABORATORIES ' 
This species is apparently, frequently identified with P. cora to 
which it has a superficial resemblance. Near conglomerate II, to P. 
arcuatus layer, Knox and Licking Counties. 
The ventral valve of P. duplicostatus was seen in connection and 
is nearly flat with a slight depression of the umbonal region but with- 
out the sharp flexture near the front seen, for example, in P. flemingi 
which is quite similar otherwise. The surface characters resemble 
those of the ventral valve, the whole surface being, however, concen- 
trically wrinkled. 
PRODUCTUS RUSHVILLENSIS, Sp. n, 
*■ (Plate III, Fig. 15.) 
Shell small, hemispherical, very tumid but abrubtly flexed near 
the middle so that the outline of ventral valve as seen from the side is 
formed of two gentle curves meeting at an angle less than a right angle 
near the middle ; length and breadth about equal ; hinge nearly equal 
to greatest width, sides intersecting the ears at nearly a right angle ; 
beak projecting but little beyond the hinge; umbo rather narrow ; in 
larger individuals a slight mesial flattening, but no sinus. Surface 
marked by few more or less distinct rounded ribs which are irregular- 
ly nodose, but simple and tend to disappear near the margin, and by 
concentric striae and folds which form strong plicati ons upon the ears ; 
spines very long, as long as the entire length of shell on the ears where 
they are numerous; surface of the cast sharply pitted and near the 
beak furrowed longitudinally. Length of medium sized specimen, 
10.5 mm., width, ii mm., height, 8 mm. Number of radiating plicae 
20. This species resembles somewhat P. wortheni of the Keokuk, but 
is still more like P. costatulus H. from the Chemung. Some forms of 
P. lachrymosa approach quite nearly. Of the described W averly forms 
none seem to require comparison except P. shumardianus of which 
the present species is the lineal descendant apparently. 
Subsequent study shows the dorsal valves to be rather strongly 
concave about one-fourth the height of tlie ventral, then nearly flat ex- 
cept for a gentle depression in the umbonal region and marked by in- 
distinct ribs below and everywhere by concentric striae and folds. 
With Phillipsia serraticaudata, Productus burlingtonensis, etc., 
(about 70 feet above horizon of P. arcuatus) at Rushville, Newark, 
Loudonville, etc. 
