638 TRANS. OF THE ACAD. OF SCIENCE. 
a few rugose plications curve around the boundaries of the 
ears on the ventral valve. 
Length, .89; breadth, .83; height of ventral valve, .55. 
From the Lower Devonian rocks of Callaway county. 
STROPHODONTA BooNENsIs, n. sp. 
Shell hemispheroidal. Ventral valve regularly convex, 
slightly raised along the mesial line ; umbo depressed, scarce- 
ly modifying the curvature of the valve; beak small, slightly 
incurved over the area; area straight, narrow, impressed, 
striated vertically, about as long as the width of the shell; 
ears small, indistinct. Dorsal valve less convex, semiellipti- 
eal, depressed in front; lateral margins recurved to meet the 
Length, 1.12; breadth, 1.20; depth of ventral valve, .69. 
This species most resembles S. injlexa ; but is shorter and 
less convex. 
Associated with the last six species in the Lower Devo- 
nian rocks of Callaway county. 
STROPHODONTA CALLAWAYENSIS, Nn. Sp. 
Shell semi-elliptical, margin regularly curved from the an- 
terior margin to the cardinal extremities. Ventral valve very 
or raised portion broadly ovate; ears large, well defined, and 
on the cardinal line. It may be distinguished from 4. eine 
costata by its larger and better defined ears, and by the ova 
form of the convex portion of the ventral valve. 
From the Hamilton rocks of Callaway county. 
