PLATE VIII. 
(Figures 1-18, 22-31 by R. P. Whitfield; 20, 21 by F. J. Swinton; 19 by G. B. Simpson.) 
Legend. D. 
A- 
F. 
F'. 
A. 
Deltidium, pedicle-valve, i 
Deltidium, brachial valve. 
Delthyrium. 
Foramen. 
Groove on delthyrium, brachial valve. 
Cardinal area : 
a. Inner portion, 
a'. Outer portion. 
b. Dental sockets, 
t. Teeth. 
j. Cardinal process, 
a. Adductor scars, 
r. Anterior diductor scars. 
r / . Posterior diductor scars. 
Genus RAFINESQUINA, gen. nov. 
(See Plate VIII, figs. 1-11; Plate IXa, tigs. 1, 2, 4; and Plate XVa, figs. 37-39.) 
Page 281. 
Rafinesquina incrassata, Stiffen'd* (not Hall). 
Fig. 1. A view of the brachial valve of a large individual; showing the area and open delthyrium of the 
pedicle-valve. 
Fig. 2. The interior of the brachial valve; showing the structure of the articulating apparatus and the 
muscular impressions. 
Fig. 3. A posterior view of the same specimen ; showing the bifurcate, incisor-shaped cardinal process, 
its surface sloping backward to the hinge-line, and partially covered by the deltidium. X 3. 
Fig. 4. A cardinal view of a portion of the hinge and area; showing the deltidia of both valves, that of 
the pedicle-valve having its surface distinctly grooved. X 3. 
Fig. 5. The internal cast of a pedicle-valve ; showing the great size of the diductor scars, and the filling 
of the foramen. 
Trenton horizon. Platteville, Wisconsin. 
Rafinesquina alternata. CoiiTad. 
7. Two views of a specimen presenting normal external characters. 
An enlargement of a portion of the hing-e-area; showing the deltidia of both valves, and the re¬ 
tention of the foramen at maturity. X 3. 
The interior of a brachial valve; showing the structure of the cardinal process and the adductor 
scars. 
The interior of a pedicle-valve ; showing the flabellate diductor and the narrow adductor scars. 
A posterior view of the articulating apparatus of the brachial valve. The incisor-shaped branches 
of the cardinal process are widely divergent, and at the bottom of the bifurcation lies a narrow 
callosity. The deltidium is well developed but not grooved in the middle, and the dental 
sockets are deeply marked. X 3. 
Hudson River group. Cincinnati, Ohio. 
For other illustrations, see Palaeontology of Ohio, Yol. I, plate vii, figs. 1-3 ; and Palaeontology of 
New York, Yol. I, plates xxjri and xxxi a. 
Genus LEPTiENA, Dalman. 
Page 276. 
Leptasna tenuistriata Sowerby (= L. rhomboidalis, Wilckens). 
Fig. 12. The interior of a brachial valve. 
Figs. 13, 14. Views of opposite sides of an individual in which the foramen is retained. 
Hudson River group. Oxford, Ohio. 
Fig. 15. A portion of the hinge of a mature individual, enlarged; showing the foramen situated in front of 
the area, the slight development of the deltidium of the pedicle-valve, and the great size of 
that of the brachial valve, the latter being deeply grooved. X 3. 
Hudson River group. Lebanon, Ohio. 
Fig. 16. An enlarged cardinal view of the central portion of the brachial valve ; showing the deep groove 
or central depression, the callosity conforming to the contour of the cardinal apophyses. 
Hudson River group. Oxford, Ohio. 
* Since the true generic relations of the Chazy species, according to the present arrangement, is not fully ascertained, 
this specific name is retained for the Trenton species. Should the original Leptcena incrassata, of the Chazy, prove to be a 
Rafinesquina, the Trenton form will retain the name of It. Minnesotensis, N. H. Winchell. 
Figs. 6, 
Fig. 8. 
Fig 9. 
Fig. 10. 
Fig. 11. 
