PLATE IV G—Continued. 
Trematis oblata, Ulrich. 
Fig. 20. The brachial valve, retaining a portion of the external ornamentation. X 2. 
From a gutta-percha cast of the original specimen (op.. (At., tig. 19). 
Hudson River group. Cincinnati, Ohio. 
SCHIZOCKANIA, Hall micl Whitfield. 
Page 142. 
SCHIZOCRANIA (?) RUD1S, ILlll. 
Fig. 21. The exterior of the brachial valve. X 2. 
Trenton limestone. Clifton, Tenn. 
SCHIZOCRANIA FILOSA, Hull. 
Fig. 22. The exterior of a brachial valve, attached to Strophomena alternate. X 2. 
Hudson River group. Cincinnati, Ohio. 
Fig. 23. The exterior of a large brachial valve. 
Fig. 24. The pedicle-valve. 
Utica slate. Mohawk Valley, N. Y. 
Fig. 25. A valve of Strophomena alternat.a, to which five of these shells are attached, all of them exposing 
the lower valve. 
The figure is taken from the Palaeontology of Ohio, vol. ii, pi. i, fig. 12, and the muscular scars on 
the internal cast of the upper valve, shown in the left of the illustration, remain as there rep- 
. resented. 
Fig. 26. An internal cast of the brachial valve ; showing the elongate, converging posterior scars, separated 
into posterior and anterior elements; also a faint median ridge extending forward beyond the 
muscular impressions. X 3. 
Fig. 27. The pedicle-valve seen on the right margin of fig. 25; showing the apical pedicle-callosity or 
incipient groove. X 2. 
Palaeontology of Ohio, vol. ii, pi. i, fig. 15. 
Fig. 28. The pedicle-area viewed from within; showing more accurately the character of the apical cal¬ 
losity, its median ridge and lateral walls indicating homology with the corresponding parts in 
the genus Orbiouloidea X 3. 
Hudson River group. Cincinnati, Ohio. 
Fig. 29. An individual from which the upper portion of the brachial valve has been removed, exposing all 
the internal characters of the pedicle-valve. X 2. 
It will be observed that in this figure, as well as in figs. 25, 33, 34 and 35, the diameter of the 
lower valve is less than that of the upper, and the former lies above and within the base of the 
latter, the attachment of the shell being largely effected by the marginal portions of the larger 
valve. 
Hudson River group. Covington, Ky. 
Fig. 30. An internal cast of a brachial valve; showing the anterior and posterior muscular scars. The 
former impressions are rarely discernible. X 1.5. 
Trenton limestone. Trenton Falls, N. F 
SCHIZOCRANIA SCHUCHERTI, Sp. 110V. 
Fig. 31. A brachial valve, retaining a portion of the external ornamentation, but showing the posterior 
muscular scars. X 3. 
Fig. 32. A smaller brachial valve’, retaining most of the exterior surface. X 3. 
Fig. 33. An individual from which most of the upper valve has been removed, exposing the pedicle-valve. 
The features of the pedicle-area are nett so clearly retained as to allow delineation. X 3. 
Hudson River group. Covington, Ky. 
SCHIZOCRANIA (?) HeLDERBERGIA, Sp. BOV. 
Fig. 34. The exterior surface of an individual; showing the pedicle-valve, its coarsely radiate and obscure 
concentric striation, and the overlapping edges of the finely striated upper valve. The character 
of the pedicle-aperture is not well retained. X 2. 
Fig. 35. The internal surface of the pedicle-valve ; showing what appears to be a broad pedicle-fissure, 
: and the overlapping margins of the upper valve. X 3. 
Lower Helderberg group. Near Clarksville, N. Y. 
