PLATE 52. 
Legend: D. Deltaria. a. Adductor scars. 
c. Crural bases. v. Vascular sinuses. 
r. Diductor scars. 
CENTRONELLA, Bitmnes. 
Page 853. 
CENTRONELLA GLANS-FAGEA, Billings. 
Figs. 1, 2, 8. Dorsal, ventral and profile views of a small specimen; showing 
the convexo-concave contour. X 3. 
Fig. 4, The interior of the umbonal portion of the brachial valve; showing 
the thickened divisions of the hinge-plate and the adductor scars. 
x 3. 
Corniferous limestone. Drift near Ann Arbor, Michigan. 
Fig. 5. An internal cast; showing the impression of the hinge-plate, dental 
sockets and muscular scars of the brachial valve. 2. 
Schoharie grit. Albany county, N. Y. 
Figs. 6,7. Two views of the loop. x5. 
Corniferous limestone. Western New York. 
TRIGERIA, Bayte. 
; Page 856. 
TRIGERIA LEPIDA, Hall. 
Figs. 8, 9, 10. Dorsal, profile and ventral views of a normal example. X 2, 
Hamilton group. Canandaigua Lake, N. Y. 
ORISKANIA, Hatt. 
Page 854. 
ORISKANIA NAVICELLA, Hall. 
Figs. 11, 12, 18. Dorsal, profile and ventral views of an average example. 
Oriskany sandstone. Rondout, N. Y. 
ROMINGERINA, Hatt. 
Page 855. 
Rosuncerina Juria, A. Winchell. 
Figs. 14, 15. Dorsal and profile views of an internal cast. 2. 
Marshall group. Pointe aux Barques, Michigan. 
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