Fig. 32 
Fig. 33. 
Fig. 34, 
Fig. 35. 
Fig. 36. 
PLATE IX—Continued. 
Orthothetes DEFOPMIS, Hall. 
. Front view of an individual retaining both valves. 
Lower Helderberg group. Borst's Mill, Schoharie county, N. Y. 
For illustrations of other species of the genus, see Palaeontology of New York, Vol, II, plate xvii, 
and ibid. Yol. IV, plates ix and x; and this volume, plate xx, figs. 8, 9. 
Genus HIPPAKIONYX, Vanuxem. 
Page 257. 
Hipparionyx proximus, Vanuxem. 
The interior of a brachial valve of a young individual; showing the strongly bifurcated process, 
high vertical crural plates, short median septum, and faint muscular scars. 
Oriskany sandstone. Cumberland, Maryland. 
. The cardinal process and its adjoining parts, as obtained from a gutta-percha impression of a 
natural cast of the interior ; natural size. This figure shows very clearly the almost complete 
obsolescence of the cardinal area, the marginal crenulations extending nearly to the base of the 
process. 
A natural cast of the interior of a pedicle-valve ; showing the impressions of the adductor and 
diductor muscles. 
The exterior of the cardinal area of the pedicle-valve ; showing the covered delthyrium and the 
projecting teeth. From a gutta-percha impression. 
Oriskany sandstone. Albany county, N. Y. 
For other illustrations, see Palaeontology of New York, Yol. Ill, plates lxxxix; xc; xci, figs. 4, 5; 
and plate xv a of this volume. 
