PLATE LVI. 
(Figures 1-13, 16-23, 28-34, 30,37, 45 by G. B. SlJU’SON; M, 15, 24-27 by K. I’. Whitfield; 35, 38 by C. E. Bekcheu; 
39-41 copies.) 
Genus RHYNCHONKLLA, Fischek de Waldheim. 
Page 177. 
Rhynchonella loxta, Fisclier lie Wuklheiiii. 
Fig’S. 1-5. Dorsal, ventral, profile, frontal and cardinal views of a noi'mal mature individual, retaining the 
smooth external sui’face, and showing the contour, acuminate median fold and spai’se lateral 
plication. 
Fig. 6. Cardinal view of an internal c^st; showing the cavity of the dental plates and median sejitum. 
This is the type of the genus Rhynchonella. 
Upper Jurassic. Oharaschoxoa, Russia. 
Genus PROTORHYNCHA, gen. nov. 
Page 180. 
PrOTORHYNCHA iEQUIRADIATA, Hall. 
Fig. 7. An internal cast of the brachial valve ; showing the length of the median septum. X 2. 
Fig. 8. The cardinal portion of the brachial valve, enlarged ; showing a clearly defined cardinal area, 
oblique dental sockets, the broad, rather ill-defined hinge-jilate, with a median cavity whose 
lateral walls are continuous with the median septum. X 3. 
Fig. 9. An internal cast of a larger pedicle-valve; showing a well defined median sinus and a very I’e- 
stricted muscular scar in the umbonal region. X 2. 
Clinton group. New Hartfoi'd, N. T. 
Genus GRTIIORIIYNCHULA, gen. nov. 
Page 181. 
Orttiorhynchula Linneyi. Nettelpoth. 
Figs. 10-12. Dorsal, profile and ventral views of tlie exterioi- of an average example; showing contour and 
character of plication. 
Fig. 13. The central portion of the cardinal region, enlarged ; showing the sharply defined cardinal area 
and the open delthyrium. X 3. 
Fig. 19. The interior of a pedicle-valve; showing the obscurely defined muscular impression, the-cardinal 
area, open delthyrium and teeth. The area has been encroached upon by the delthyrium and 
consequently diminished in size. 
Hudson River group. Na.'ilivllJe, Tennessee. 
The original specimens of this species are fi'om Danville and neigboring localities, Kentucky. 
Genus RHYNCIIOTREMA. Hall. 
Page 182. 
Rhynchotreima capax, Conrad. 
Figs. 14, 15. Dorsal and frontal views of a somewhat gibbous adult; showing the character of the plication 
and the fine concentric lineation. 
Hudson River group. Frankfort, Kentucky. 
Fig. 1(). The interior of a pediclC'-valve; showing the thickened deltidial plates consolidated with the 
valve, the deep pedicle and muscular cavity, and recurved teeth. 
Hudson River group. Richmond, Indiana. 
Fig. 17. The interior of a pedicle-valve; showing the broad, concave deltidial plates, in contact for their entire 
length along the median line, greatly thickened and consolidated with the bottom of the valve 
beneath ; also the recurved teeth resting upon the thickened lateral walls, the pair of shallow 
depressions in the umbonal i-egion and the deep diductor scar in the middle of the valve, which 
has been greatly encroached upon by the umbonal thickening of the shell. 
Fig. 18. An enlargement of the umbonal portion of the same specimen. The small cavity at the base of the 
deltidial plates is the inner opening of the pedicle-passage which was functional at this advanced 
growth-stage of the shell, its outer opening being on the back of the umbo, considerably 
removed from the beak, and connected with the apex by a groove whose margins ai’e shown 
in the figure. (For more complete illustration of this structure, see supplementary plate.) 
Fig. 20. The interior of an incomplete brachial valve; showing the hinge-plate, cardinal process and 
meilian septum. 
