EXPLANATION OF PLATE X. 



(Figures all of natural size.) 



Cyrtina '.' Curupira, Rathbim, sp. nov., page 242. 



1 and 6. Dorsal valves. 



Retzia Wardiana, Hartt, sp. nov., page 245. 

 3, 4, 5, 8, 11, 12 and 14. Ventral- valves. 



16. Ventral valve, with the plications finer and more numerous than in the 

 majority of specimens. 



2 and 9. Dorsal valves. 



Orthis Nettoana, Rathhun, sp. nov., page 247. 



7 and 13. Ventral valves. 

 10. Dorsal valve. 



Terebratiila Derbyaiia, Hartt, sp. nov., pagt 236. 

 15, IS, 24 and 25. Ventral valves. 



17, 19, 21 and 22. Dorsal view of specimens of which both valves are 



preserved. The beaks of the ventral valves are seen extending 

 beyond the dorsal valves, but in all the specimens tlifv arc ihotc or 

 less defective. 

 20. Dorsal valve. 



Tropitloleptus eariiiatus, Con., (sp.,) page 254. 



26. Exterior mould of dorsal valve, very much broken. 



Retzia Janiesiana^ Hartt, sp. nov., page 248. 



29, 83, 34, 86, 37 and 38. Ventral valves, showing tlie enlarged lucdiaii 

 depression. ' ' 



27, 28, 31, 82 and 35. Dorsal valves. 



80. View of dorsal valve of a specimen in whicli l)oth valves are pre- 

 served. The beak of ventral valve is slightly extended beyond tlie 

 doi'sal valve. 



23. Dorsal view of a rather narrow specimen, of which the ventral valve 

 is also preserved. The plications are less in number than usual. 



Clioiietes Herbert-Siiiithiij Hartt, sp. nov., page 251. 



39, 41, 42 and 46. Ventral valves of ordinary size. 



44. Ventral valve, same as above, but smooth from tlie character of the 

 rock in which it occurred. 



40. Ventral valve, rather above the average size. 

 45 and 47. Exterior moulds of dorsal valves. 



Clioiietes Onettiana, Rathhun, sp. nov., page 253. 



43 and 48. Ventral valves, with nearly smooth surfaces and sliowhig the 

 short median septum very distinctly. 



(Exce])t where otherwise stated, the above specimens are all of interior 

 moulds.) 



