ADDENDA. 
Orthis stropliomenoides. 
Plate XXIII. Fig. 7 a, b, d,f, g. 
For explanation of these figures, which illustrate more completely the character 
of the species, see explanation accompanying Plate xxiii, volume of plates. 
Orthis cnmhcrlandia (n. s ). 
Plate XCY A. Fig. 20 & 21. 
Shell large, suborbicular, depressed. Ventral valve depressed convex in 
the middle and towards the beak, flattened or scarcely concave towards 
the front : area narrow and short; foramen large; dental lamellae 
thin ; muscular area broadly flabelliform. 
The surface externally marked by numerous fine sharp striae, which are 
increased by interstitial additions. 
This species approaches the 0. tubulostriata in many of its characteristics, but is 
sufficiently distinct to be easily identified, the strise being finer and the beak less 
prominent. It has the form of muscular impression common to O. oblata and others 
while it is a thinner shell with more prominent strise. 
Fig. 20. The exterior of a ventral valve of this species. 
Fig. 21. The interior of a smaller ventral valve of the same. 
Geological position and locality. In the Oriskany sandstone : Cumberland, Md. 
[ Paleontology III.] 61 
