PLATE LXXXIII. 
(Figures 1-8,12, 13, 26-41 by G. B. SiJiPSON ; 9 by C. E. Beechek ; in, 11 by 11. P. Whitfield ; 11-23 by E Emmons ) 
Genus EICHWALDIA, Billings. 
Page 307. 
Eiciiwaluia subtrigonalis, Billings. 
Fig. 1. Dorsal view of conjoined valves, the brachial valve being so broken as to expose the median 
septum. 
Figs. 2-4. Dorsal, cardinal and front views; showing the smooth surface, and the “bare spot,” or ped¬ 
icle apertui'e. d'hese figures are from the original specimens of the sjiecies. 
Black River limestone. Pauquette’s Papids, Canada. 
Eichwaldia concinna, Hall. 
Fig. 5. Dorsal view of the original specimen. 
Niagara gi-oup. Perry county, Tennessee. 
Prchwaldia gibbosa, Hall. 
Fig. 6. Dorsal view of the original specimen. 
Fig. 7. An enlargement of the external surface, showing the punctie. X 5. 
Niagara group. Perry county, Tennessee. 
Eichwaldia reticulata, Hall. 
Fig. 8. The interior of the umbonal portion of the pedicle-valve ; showing the triangular internal apical 
plate. X 2. 
Fig. 9. Dorsal view of the youngest specimen observed. X 10. (After Beecher and Clarke, Memoirs 
N. Y. State Museum, Vol. 1, No. 1.) 
Figs. 10, 11. Cardinal and dorsal views of an average specimen; showing the pedicle-aperture and the 
character of the external surface. X 2. 
Fig. 12. The interior of the pedicle-valve ; showing the open delthyrium and the linear ridges on the lat¬ 
eral margins. X 2. 
Fig. 13. The interior of a brachial valve ; showing the cardinal jirocess and the marginal grooves for the 
reception of the ridges on the o^iposite valve. X 2. 
Niagara group. Waldron, Indiana. 
Genus AULACOBHYNCHUS, Dittjuar. 
Page 311. 
Aulacorhynchus millepunctatus, Meek and VYortlieu. 
The exterior of a pedicle-valve, from which a portion of the shell has been exfoliated, showing the 
inner surface of the triangular muscular platform. 
A very large brachial valve; showing the outline and surface characters. 
Coal Measures. Crooked Creek, Illinois. 
Genus TBIPLECIA, Hall. 
Part 1, page 269. 
Triplecia Niagarensis, sp. nov. 
Figs. 16-19. Cardinal, profile, oblique cardinal and front views of an internal cast; showing the sharply 
defined median fold and sinus on brachial and pedicle-valves respectively, the marginal plica¬ 
tion, and the cavity left by the cardinal pn cess. 
Fig. 20. View of the articulating processes, taken from a gutta-percha impression of the same specimen ; 
showing the bifurcated cardinal process lind the teeth. X 5. 
Niagara dolomites. Near Milwaukee, Wisconsin. 
Fig. 14. 
Pig. 15. 
