PLATE LVII. 



(Figures 1-50 by B. P. Whitfield; 51-54 by E. Emmons.) 



Genus CAMAROTCECHIA, gen. nov. 



Page 189. 



CAMAROTfECHiA Tethys, Billings. 

 Figs. 1, 2. Cardinal and profile views of a rather large shell. 



Corniferous limestone. Province of Ontario. 



Camarotcechia Billinqsi, Hall. 



Fig. 3. Doraal view of an internal cast ; showing the position of the median septum. 

 Corniferous limestone. Western New York. 



Camarotcechia Carolina, Hall. 



Figs. 4, 5. Dorsal and cardinal views of a partially exfoliated specimen. 

 Fig. 6. Front view of a more gibbous shell. 



Corniferous limestone. SaTidusky, 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, vCntral, cardinal, profile and frontal views of a large and typical example. 

 Hamilton group. Western New York. 



Camarotcechia congregata. Hall. 



Pigs. 15-19. Dorsal, ventral, cardinal, frontal and profile views of a large individual. 



Fig. 20. Cardinal view of an internal cast ; showing the cavities of the dental plates and median septum. 



Fig. 21. An internal cast of the pedicle-valve ; showing a lai-ge diductor impression. 



Fig. 22. A similar cast of the interior with the muaculai' ai-ea more restricted. 



Pig. 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 portion of the brachial valve ; showing the 

 filling of the incipient spondylium and the crenulation of the outer socket-walls. 



FigB. 26, 27. The same parts drawn from gutta percha impressions taken from natural casts of other indi- 

 viduals ; showing the broad hinge-plate with its median division terminating in a spondylium, 

 which is supported by branches of the median septum. 



Hamilton group. Varioiis 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 plicalions on the median fold. 

 Chemung gfroup. 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 spondy- 

 lium and the length of the median septum. 



Chemung group. Bradford county, Pennsylvania. 



