PLATE LVII. 



(Figures 1-50 by R. P. \VHirriEi.D; 51-54 by E. Emmons.) 



Genus CAMAROTCECHIA. gen. no v. 



I'aRC 1S9. 



Camarotcechta Tethys, Billin_2;.s. 



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



Coriiifei'ous limestone. Province of Ontario. 



Camarot(echia Billinqsi, Hall. 



Fiu;. 3. Porsal view of an internal cast ; showing the position of the median septum. 

 Corniferous limestone. Westei-n New York. 



Camarot(echia Carolina, Hall. 



Fig-s. 4, 5. Dorsal and cardinal views of a partially exfoliated specimen. 

 Fig. 6. Front view of a moi'e gibbous shell. 



Corniferous limestone. iSandiisky, 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. Dor.sal, ventral, cardinal, profile and frontal views of a large and typical example. 

 Hamilton group. Western New York. 



CAMAROTOiCHIA CONGRE(iATA, Hall. 

 Figs. 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 jiedicle-valve ; showing a large diductor impression. 

 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 tilling 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 outei' socket-walls. 

 Figs. 26, 27. The same parts drawn from gutta jiercha 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. Various 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 gi'oup. Central a7id western New Ym-k. 



Camarotcechia Stevensi (^ Rhynchonella Stephani), Hall. 



Fig. 33. An internal cast of the pedicle-valve. 



Pigs. 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 septimi. 



Chemung group. Bradford county. Pennsylvania. 



