PLATE LVin—Continued. 
Subgenus PLETHORHYNCHA, s.-gen. nov. 
Page 191. 
Plethokhyncha speoiosa, Hull. 
Figs. 29-31. Cardinal, front and profile views of a large entire individual; showing the robust form of the 
shell, its subquadrate transverse section, serrate margins and broad, somewhat concave lateral 
slopes. The abrupt marginal extensions of the cardinal slopes of the pedicle-valve, fitting 
into corresponding excavations of the brachial valve, as shown in figures 29 and 30, are the 
thickened teeth which are cemented to the walls of the shell throughout their entire extent and, 
at their summits only, fitted into shallow sockets in the opposite valve. 
Fig. 32. The interior of a brachial valve, slightly broken about the margins ; showing a thickened, undi¬ 
vided hinge-jdate, bilobed cardinal process, narrow dental sockets and the median septum. 
Fig. 33. A cardinal view of the same specimen ; showing the elevation of the cardinal process and crura 
and the marginal excavations for the reception of the teeth. 
Fig. 34. Cardinal view of the umbonal portion of an old shell in which the entire hinge-plate has become 
greatly thickened and elevated, and the ajiical portion or cardinal process resorbed and exca¬ 
vated. The projecting points above are the bases of the crura. 
Fig. 35. The interior of a small pedicle-valve ; showing the foi-rn of the teeth, and faint median muscular 
ridge on the bottom of the valve. 
Fig. 36. The intei’ior of a young brachial valve in which the hinge-jilate is divided, its lateral portions rest¬ 
ing on the median septum, and the cardinal margins but slightly excavated for the reception of 
the teeth. 
Fig. 37. The umbonal portion of the same specimen, enlarged ; showing the small cardinal process and the 
median division of the hinge-plate resting on the septum and forming an incipient spondylium. 
X 2. 
Oriskany sandstone. Cumberland, Maryland. 
Genus UNCINULUS, Bayle. 
Page 195. 
Uncinulus (Uncinulina) Stricklandi, Sowei’by. 
Fig. 38. Cardinal view of an internal cast of both valves, the brachial valve being represented above ; 
showing the cavities representing the median septum, the cardinal process and hinge-plate, 
and the ridge filling the median division of the latter. 
Niagara dolomites. Near Milwaukee, Wisconsin. 
Figs. 39, 40. Dorsal and cardinal views of the exterior of a normal adult; showing the low median fold and 
the smooth cardinal slopes. 
Niagara group. Waldron, Indiana. 
