CYRTINA, Davipson. 
Page 763. 
Cyrtmva Hamittonensis, Hall. 
Fig. 12. An internal cast of the pedicle-valve; showing the position of the 
median septum. 
Fig. 18. An axial section of combined valves; showing the form of the median 
septum and the supported dental plate. 
Fig. 17. The interior of a brachial valve; showing the articulating processes. 
fig. 19, A portion of a transverse section of the umbonal region of the pedicle- 
valve; showing the deltarium and the dental lamellz thickened at 
their union with the median septum, the edge of the latter extending 
into the deltidial cavity. x3. 
Hamilton group. Localities in Western New York. 
Cyatina HAMILTONENSIS, var. RECTA, Hall. 
Figs, 14, 15. Views of anormal example; showing the high, erect cardinal area. 
Hamilton group. Western New York. 
Cyrtina CURVILINEATA, White. 
Fig. 16. Dorsal view of a large specimen; showing the plicated median fold of 
the brachial valve and the distorted umbo of the pedicle-valve. 
Hamilton group. Jowa City, Iowa. 
Cyrtina AcuTrrostris, Shumard. 
Fig. 18. Cardinal view of a normal example. ’ 
Choteau limestone. Pike county, Missouri. 
CYRTINA TRIQUETRA, Hall. 
Fig. 20. Ventral view of an average example; showing the curvature of the 
umbo. 
Hamilton group. Rock Island, Iilinois. 
CyRiina LacHRyMosa, Hall. 
Fig. 21. Ventral view of an average example; showing the pustulose surface. 
Waverly group. Richfield, Ohio. 
Cyrtina BrexicaTa, Hall. 
Figs. 22, 28. Cardinal and front views; showing the imperforate deltarium and 
smooth exterior. 
Schoharie grit. Schoharie, N. Y. 
Cyrrina umBonaTa, var. ALPENENSIS, Hall. 
Fig. 24. Cardinal view of a normal mature individual. 
Figs. 25, 26. Dorsal and lateral views of a preparation; showing the form 
of the spiral cones and jugum, and the extent of the median 
septum. X11. 
Hamilton group. Alpena, Michigan. 
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