OF DENISON UNIVERSITY. 
45 
cardinal area arched, striate parallel to the hinge line, foramen ^ to 
1-5 as wide as the hinge ; mesial sinus rather narrow and ill-defined, 
triangular in section, continuing to the beak ; interior with short, di- 
verging dental lamellae and small rostral cavity. Dorsal valve quite 
flat, except the rather low, ill-defined, triangular fold ; beak projecting 
beyond the hinge-line; area narrow, striate at right angles to hinge-tine. 
Surface of both valves covered by numerous small, low, rounded cos- 
tae, which bifurcate somewhat irregularly and are marked by numer- 
ous radiating striae and, less obviously, by concentric stride as well as 
the usual lines of growth. (The cancellated appearance spoken of 
by Meek is rarely observed, while the radiating striations are quite 
noticeable. Sixty-five to seventy-five costae are found on a valve of 
medium size, from eight to fifteen occupying fold and sinus. The 
typical form is found near the summit of the Waverly, about 100 feet 
above congl. II, with Productus seniireticulatus. This layer occurs at 
at the very top of the exposure at Rushville and cannot be far below 
the Chester limestone. 
In conglomerate I, are found specimens apparently intermediate 
between the previous species and S. striatiformis, but more convex than 
either. In the free stone still above is another variety which is with 
less doubt referred to S. striatiformis. Specimens are figured on Plate 
VI, Figs. 6, 7. These have a broader sinus and more nearly quadrate 
form, though short mucronate ears are retained. 
If S. centronata is a valid name for the form from Cuyahoga shales 
the relation between that species and S. marionensis must be left for 
future study. The close relation of all these to S. disjuncta of the Che- 
mung is noteworthy. 
Spirifer hiplicatus, Hall. 
Not Spirifer biplicatus, Meek, O. Pal. Vol II. 
But a single dorsal valve has been encountered with the characters 
of S. biplicatus, indeed, we suspected the validity of the species. It 
may be confessed that a wider range of observation may invalidate the 
assumed distinctions. This dorsal valve differs from those of S. stri- 
atiformis, with which it is associated, in the greater distinctness of the 
plicae, and the depressions bordering the median fold, and by the fact 
that the plicae on the fold are so much smaller than those of the rest 
