PLATE LVII. 
(Figures 1-50 by B. P. Whitfield; 51-54 by E. Emmons.) 
Genus CAMAROTCECHIA, gen. nov. 
Page 189. 
Camaeotcechia Tetitts, Billings. 
Figs. 1, 2. Cardinal and profile views of a rather large shell. 
Corniferous limestone. Province of Ontario. 
Camarotcechia Billingsi, Hall. 
Fig. 3. Dorsal view of an internal cast; showing the position of the median septum. 
Corniferous limestone. Western New YorJc. 
Camarot(echia Caroeina, Hall. 
Figs. 4, 5. Dorsal and cardinal views of a xiartially exfoliated s^iecimen. 
Fig. 6. Front view of a more gibbous shell. 
Corniferous limestone. Sandusky, Ohio. 
Camarotcechia Horsfordi, Hall. 
Figs. 7-9. Cardinal, frontal and profile views of a typical mature individual. 
Hamilton shales. Moscow, N. Y. 
Camarotcechia Sappho, Hall. 
Figs. 10-14. Dorsal, ventral, cardinal, pi-otile and frontal views of a large and typical examjjle. 
Hamilton grouj). Western New York. 
Camarotcechia congregata. Hall. 
Figs. 15-19. Dorsal, ventral, carilinal, frontal and i)rotile views of a large individual. 
Fig. 20. Cardinal view of an internal cast; showing the cavities of the dental jilates and median septum. 
Fig. 21. An internal cast of the iiedicle-valve ; showing a large diductor imjiression. 
Fig. 22. A similar cast of the interior with the muscular area more restricted. 
Fig. 23. An internal cast of a brachial valve ; showing the length of the median septum, the filling of the 
cardinal cavity and the scars of the adductor muscles. 
Figs. 24, 25. Enlargements of the internal casts of the umbonal x)ortion of the brachial valve ; showing the 
filling of the incipient s^iondylium and the ci’ennlation of the outer socket-walls. 
Figs. 26, 27. The same parts drawn from gutta percha impressions taken from natui-al casts of other indi¬ 
viduals ; showing the broad hinge-xilate with its median division terminating in a siiondylium, 
which is sux)X)orted by branches of the median septum. 
Hamilton group. Vai-ious localities in the sandy shales of Schoharie, Otsego and Madi¬ 
son counties, N. Y. 
Camarotcechia contracta. Hall. 
Figs. 28, 29, 31. Dorsal, profile and frontal views of an internal cast. 
Figs. 30, 32. Dorsal and cardinal views of a cast with coarser plications on the median fold. 
Chemung grouji. Central and western New York. 
Camarotcechia Stevensi (==: Rhynchonella Stephani), Hall. 
Fig. 33. An internal cast of the pedicle-valve. 
Figs. 34, 35. Dorsal and cardinal views of a cast of the brachial valve ; showing the filling of the syiondy- 
lium and the length of the median septum. 
Chemung group. Bradford county, PeJinsylvania. 
