640 TRANS. OF THE ACAD. OF SCIENCE. 
long as the width of the shell. Surface marked with small, 
rounded, bifurcating plications, rendered granulose by obso- 
lete concentric striz. 
Length, 1.12; width, 1.09; thickness, .43. 
This fossil most resembles O. Vanuxemi of Prof. Hall; 
but it is more convex towards the beaks, and more flattened 
towards the anterior border; has a wider area and much finer 
striz. 
Rare in the Chemung rocks of Cooper and Marion counties. 
Propuctus CALLAWAYENSIS, Nn. sp. 
Shell small, thin, depressed, spinose, varying from semi- 
orbicular to suborbicular. Ventral valve very regularly con- 
ex, but most so on the umbo, flattened towards the ears; 
beak small, incurved to or slightly over the cardinal line; 
umbo small, prominent, projecting a little back of the cardi- 
nal line; ears large flattened triangular, slightly arched to- 
wards the cardinal line, rounded on the outer angle; mest 
sinus obsolete, or entirely wanting. Dorsal valve regularly 
concave, most depressed in the middle in adult specimens, 
but nearer the beak in the young; ears well defined, trian- 
gular, slightly arched; cardinal line as long or shorter than 
the width of the shell; curved at the extremities towards 
the lateral margins and down towards the center of the ven- 
tral valve. Surface marked with small, irregular, interrupted 
corrugations and strie ; both valves thickly set with depres- 
sed spines, whose bases are more or less prolonged into Jong- 
tudinal plications; spinus on the dorsal valve, smaller. 
Length, .85; breadth, 1.12; thickness, .40. 
Abundant in the Lower Devonian rocks of Callaway coun- 
ty, associated with Nautilus Lawsii, Strophodonta navalis, 
and S. Kemperi. 
Propuctus CoporRENSIS, Nn. sp. 
arked ric corrugations, 
and by broad, unequal, irregular, obsolete, longitudinal ne 
few scattered spines. 
Length, .75; breadth, .58; thickness, .41. 
This shell most resembles the P. arcuatus of Prof. Hall, 
